diff --git a/news/6638.feature b/news/6638.feature
new file mode 100644
index 00000000000..f96b9133d29
--- /dev/null
+++ b/news/6638.feature
@@ -0,0 +1,2 @@
+Add a new command ``pip debug`` that can display e.g. the list of compatible
+tags for the current Python.
diff --git a/src/pip/_internal/cli/base_command.py b/src/pip/_internal/cli/base_command.py
index 65842043373..53b4cf73aab 100644
--- a/src/pip/_internal/cli/base_command.py
+++ b/src/pip/_internal/cli/base_command.py
@@ -324,10 +324,7 @@ def _build_package_finder(
         self,
         options,               # type: Values
         session,               # type: PipSession
-        platform=None,         # type: Optional[str]
-        py_version_info=None,  # type: Optional[Tuple[int, ...]]
-        abi=None,              # type: Optional[str]
-        implementation=None,   # type: Optional[str]
+        target_python=None,    # type: Optional[TargetPython]
         ignore_requires_python=None,  # type: Optional[bool]
     ):
         # type: (...) -> PackageFinder
@@ -346,13 +343,6 @@ def _build_package_finder(
             ignore_requires_python=ignore_requires_python,
         )
 
-        target_python = TargetPython(
-            platform=platform,
-            py_version_info=py_version_info,
-            abi=abi,
-            implementation=implementation,
-        )
-
         return PackageFinder.create(
             search_scope=search_scope,
             selection_prefs=selection_prefs,
diff --git a/src/pip/_internal/cli/cmdoptions.py b/src/pip/_internal/cli/cmdoptions.py
index eba545c8509..ac41bd99bd4 100644
--- a/src/pip/_internal/cli/cmdoptions.py
+++ b/src/pip/_internal/cli/cmdoptions.py
@@ -22,6 +22,7 @@
 from pip._internal.models.format_control import FormatControl
 from pip._internal.models.index import PyPI
 from pip._internal.models.search_scope import SearchScope
+from pip._internal.models.target_python import TargetPython
 from pip._internal.utils.hashes import STRONG_HASHES
 from pip._internal.utils.misc import redact_password_from_url
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -356,6 +357,7 @@ def find_links():
 
 
 def make_search_scope(options, suppress_no_index=False):
+    # type: (Values, bool) -> SearchScope
     """
     :param suppress_no_index: Whether to ignore the --no-index option
         when constructing the SearchScope object.
@@ -600,6 +602,26 @@ def _handle_python_version(option, opt_str, value, parser):
 )  # type: Callable[..., Option]
 
 
+def add_target_python_options(cmd_opts):
+    # type: (OptionGroup) -> None
+    cmd_opts.add_option(platform())
+    cmd_opts.add_option(python_version())
+    cmd_opts.add_option(implementation())
+    cmd_opts.add_option(abi())
+
+
+def make_target_python(options):
+    # type: (Values) -> TargetPython
+    target_python = TargetPython(
+        platform=options.platform,
+        py_version_info=options.python_version,
+        abi=options.abi,
+        implementation=options.implementation,
+    )
+
+    return target_python
+
+
 def prefer_binary():
     # type: () -> Option
     return Option(
diff --git a/src/pip/_internal/cli/main_parser.py b/src/pip/_internal/cli/main_parser.py
index 767f35d50ee..6d0b719aa42 100644
--- a/src/pip/_internal/cli/main_parser.py
+++ b/src/pip/_internal/cli/main_parser.py
@@ -4,7 +4,6 @@
 import os
 import sys
 
-from pip import __version__
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.parser import (
     ConfigOptionParser, UpdatingDefaultsHelpFormatter,
@@ -13,7 +12,7 @@
     commands_dict, get_similar_commands, get_summaries,
 )
 from pip._internal.exceptions import CommandError
-from pip._internal.utils.misc import get_prog
+from pip._internal.utils.misc import get_pip_version, get_prog
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
@@ -39,12 +38,7 @@ def create_main_parser():
     parser = ConfigOptionParser(**parser_kw)
     parser.disable_interspersed_args()
 
-    pip_pkg_dir = os.path.abspath(os.path.join(
-        os.path.dirname(__file__), "..", "..",
-    ))
-    parser.version = 'pip %s from %s (python %s)' % (
-        __version__, pip_pkg_dir, sys.version[:3],
-    )
+    parser.version = get_pip_version()
 
     # add the general options
     gen_opts = cmdoptions.make_option_group(cmdoptions.general_group, parser)
diff --git a/src/pip/_internal/commands/__init__.py b/src/pip/_internal/commands/__init__.py
index 2e90db34f69..9e0ab86b9ca 100644
--- a/src/pip/_internal/commands/__init__.py
+++ b/src/pip/_internal/commands/__init__.py
@@ -5,6 +5,7 @@
 
 from pip._internal.commands.completion import CompletionCommand
 from pip._internal.commands.configuration import ConfigurationCommand
+from pip._internal.commands.debug import DebugCommand
 from pip._internal.commands.download import DownloadCommand
 from pip._internal.commands.freeze import FreezeCommand
 from pip._internal.commands.hash import HashCommand
@@ -36,6 +37,7 @@
     WheelCommand,
     HashCommand,
     CompletionCommand,
+    DebugCommand,
     HelpCommand,
 ]  # type: List[Type[Command]]
 
diff --git a/src/pip/_internal/commands/debug.py b/src/pip/_internal/commands/debug.py
new file mode 100644
index 00000000000..99b5b946f8a
--- /dev/null
+++ b/src/pip/_internal/commands/debug.py
@@ -0,0 +1,102 @@
+from __future__ import absolute_import
+
+import logging
+import sys
+
+from pip._internal.cli import cmdoptions
+from pip._internal.cli.base_command import Command
+from pip._internal.cli.cmdoptions import make_target_python
+from pip._internal.cli.status_codes import SUCCESS
+from pip._internal.utils.logging import indent_log
+from pip._internal.utils.misc import get_pip_version
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.wheel import format_tag
+
+if MYPY_CHECK_RUNNING:
+    from typing import Any, List
+    from optparse import Values
+
+logger = logging.getLogger(__name__)
+
+
+def show_value(name, value):
+    # type: (str, str) -> None
+    logger.info('{}: {}'.format(name, value))
+
+
+def show_sys_implementation():
+    # type: () -> None
+    logger.info('sys.implementation:')
+    if hasattr(sys, 'implementation'):
+        implementation = sys.implementation  # type: ignore
+        implementation_name = implementation.name
+    else:
+        implementation_name = ''
+
+    with indent_log():
+        show_value('name', implementation_name)
+
+
+def show_tags(options):
+    # type: (Values) -> None
+    tag_limit = 10
+
+    target_python = make_target_python(options)
+    tags = target_python.get_tags()
+
+    # Display the target options that were explicitly provided.
+    formatted_target = target_python.format_given()
+    suffix = ''
+    if formatted_target:
+        suffix = ' (target: {})'.format(formatted_target)
+
+    msg = 'Compatible tags: {}{}'.format(len(tags), suffix)
+    logger.info(msg)
+
+    if options.verbose < 1 and len(tags) > tag_limit:
+        tags_limited = True
+        tags = tags[:tag_limit]
+    else:
+        tags_limited = False
+
+    with indent_log():
+        for tag in tags:
+            logger.info(format_tag(tag))
+
+        if tags_limited:
+            msg = (
+                '...\n'
+                '[First {tag_limit} tags shown. Pass --verbose to show all.]'
+            ).format(tag_limit=tag_limit)
+            logger.info(msg)
+
+
+class DebugCommand(Command):
+    """
+    Display debug information.
+    """
+
+    name = 'debug'
+    usage = """
+      %prog <options>"""
+    summary = 'Show information useful for debugging.'
+    ignore_require_venv = True
+
+    def __init__(self, *args, **kw):
+        super(DebugCommand, self).__init__(*args, **kw)
+
+        cmd_opts = self.cmd_opts
+        cmdoptions.add_target_python_options(cmd_opts)
+        self.parser.insert_option_group(0, cmd_opts)
+
+    def run(self, options, args):
+        # type: (Values, List[Any]) -> int
+        show_value('pip version', get_pip_version())
+        show_value('sys.version', sys.version)
+        show_value('sys.executable', sys.executable)
+        show_value('sys.platform', sys.platform)
+        show_sys_implementation()
+
+        show_tags(options)
+
+        return SUCCESS
diff --git a/src/pip/_internal/commands/download.py b/src/pip/_internal/commands/download.py
index abdd1c2d01b..5642b561758 100644
--- a/src/pip/_internal/commands/download.py
+++ b/src/pip/_internal/commands/download.py
@@ -5,6 +5,7 @@
 
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.base_command import RequirementCommand
+from pip._internal.cli.cmdoptions import make_target_python
 from pip._internal.legacy_resolve import Resolver
 from pip._internal.operations.prepare import RequirementPreparer
 from pip._internal.req import RequirementSet
@@ -69,10 +70,7 @@ def __init__(self, *args, **kw):
             help=("Download packages into <dir>."),
         )
 
-        cmd_opts.add_option(cmdoptions.platform())
-        cmd_opts.add_option(cmdoptions.python_version())
-        cmd_opts.add_option(cmdoptions.implementation())
-        cmd_opts.add_option(cmdoptions.abi())
+        cmdoptions.add_target_python_options(cmd_opts)
 
         index_opts = cmdoptions.make_option_group(
             cmdoptions.index_group,
@@ -96,13 +94,11 @@ def run(self, options, args):
         ensure_dir(options.download_dir)
 
         with self._build_session(options) as session:
+            target_python = make_target_python(options)
             finder = self._build_package_finder(
                 options=options,
                 session=session,
-                platform=options.platform,
-                py_version_info=options.python_version,
-                abi=options.abi,
-                implementation=options.implementation,
+                target_python=target_python,
             )
             build_delete = (not (options.no_clean or options.build_dir))
             if options.cache_dir and not check_path_owner(options.cache_dir):
diff --git a/src/pip/_internal/commands/install.py b/src/pip/_internal/commands/install.py
index 6898cb276db..9532ef88fe9 100644
--- a/src/pip/_internal/commands/install.py
+++ b/src/pip/_internal/commands/install.py
@@ -12,6 +12,7 @@
 from pip._internal.cache import WheelCache
 from pip._internal.cli import cmdoptions
 from pip._internal.cli.base_command import RequirementCommand
+from pip._internal.cli.cmdoptions import make_target_python
 from pip._internal.cli.status_codes import ERROR
 from pip._internal.exceptions import (
     CommandError, InstallationError, PreviousBuildDirError,
@@ -114,10 +115,7 @@ def __init__(self, *args, **kw):
                  '<dir>. Use --upgrade to replace existing packages in <dir> '
                  'with new versions.'
         )
-        cmd_opts.add_option(cmdoptions.platform())
-        cmd_opts.add_option(cmdoptions.python_version())
-        cmd_opts.add_option(cmdoptions.implementation())
-        cmd_opts.add_option(cmdoptions.abi())
+        cmdoptions.add_target_python_options(cmd_opts)
 
         cmd_opts.add_option(
             '--user',
@@ -285,13 +283,11 @@ def run(self, options, args):
         global_options = options.global_options or []
 
         with self._build_session(options) as session:
+            target_python = make_target_python(options)
             finder = self._build_package_finder(
                 options=options,
                 session=session,
-                platform=options.platform,
-                py_version_info=options.python_version,
-                abi=options.abi,
-                implementation=options.implementation,
+                target_python=target_python,
                 ignore_requires_python=options.ignore_requires_python,
             )
             build_delete = (not (options.no_clean or options.build_dir))
diff --git a/src/pip/_internal/models/target_python.py b/src/pip/_internal/models/target_python.py
index e10efb8ea32..7ad5786c435 100644
--- a/src/pip/_internal/models/target_python.py
+++ b/src/pip/_internal/models/target_python.py
@@ -5,7 +5,8 @@
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
-    from typing import Optional, Tuple
+    from typing import List, Optional, Tuple
+    from pip._internal.pep425tags import Pep425Tag
 
 
 class TargetPython(object):
@@ -54,9 +55,32 @@ def __init__(
         self.py_version_info = py_version_info
 
         # This is used to cache the return value of get_tags().
-        self._valid_tags = None
+        self._valid_tags = None  # type: Optional[List[Pep425Tag]]
+
+    def format_given(self):
+        # type: () -> str
+        """
+        Format the given, non-None attributes for display.
+        """
+        display_version = None
+        if self._given_py_version_info is not None:
+            display_version = '.'.join(
+                str(part) for part in self._given_py_version_info
+            )
+
+        key_values = [
+            ('platform', self.platform),
+            ('version_info', display_version),
+            ('abi', self.abi),
+            ('implementation', self.implementation),
+        ]
+        return ' '.join(
+            '{}={!r}'.format(key, value) for key, value in key_values
+            if value is not None
+        )
 
     def get_tags(self):
+        # type: () -> List[Pep425Tag]
         """
         Return the supported tags to check wheel candidates against.
         """
diff --git a/src/pip/_internal/utils/misc.py b/src/pip/_internal/utils/misc.py
index 91adf17ddb9..c9d6894533f 100644
--- a/src/pip/_internal/utils/misc.py
+++ b/src/pip/_internal/utils/misc.py
@@ -28,6 +28,7 @@
 from pip._vendor.six.moves.urllib import request as urllib_request
 from pip._vendor.six.moves.urllib.parse import unquote as urllib_unquote
 
+from pip import __version__
 from pip._internal.exceptions import CommandError, InstallationError
 from pip._internal.locations import (
     running_under_virtualenv, site_packages, user_site, virtualenv_no_global,
@@ -104,6 +105,18 @@ def cast(typ, val):
     logger.debug('lzma module is not available')
 
 
+def get_pip_version():
+    # type: () -> str
+    pip_pkg_dir = os.path.join(os.path.dirname(__file__), "..", "..")
+    pip_pkg_dir = os.path.abspath(pip_pkg_dir)
+
+    return (
+        'pip {} from {} (python {})'.format(
+            __version__, pip_pkg_dir, sys.version[:3],
+        )
+    )
+
+
 def normalize_version_info(py_version_info):
     # type: (Optional[Tuple[int, ...]]) -> Optional[Tuple[int, int, int]]
     """
diff --git a/tests/functional/test_debug.py b/tests/functional/test_debug.py
new file mode 100644
index 00000000000..3f5374722da
--- /dev/null
+++ b/tests/functional/test_debug.py
@@ -0,0 +1,50 @@
+import pytest
+
+from pip._internal import pep425tags
+
+
+@pytest.mark.parametrize(
+    'args',
+    [
+        [],
+        ['--verbose'],
+    ]
+)
+def test_debug(script, args):
+    """
+    Check simple option cases.
+    """
+    args = ['debug'] + args
+    result = script.pip(*args)
+    stdout = result.stdout
+
+    assert 'sys.executable: ' in stdout
+    assert 'sys.platform: ' in stdout
+    assert 'sys.implementation:' in stdout
+
+    tags = pep425tags.get_supported()
+    expected_tag_header = 'Compatible tags: {}'.format(len(tags))
+    assert expected_tag_header in stdout
+
+    show_verbose_note = '--verbose' not in args
+    assert (
+        '...\n  [First 10 tags shown. Pass --verbose to show all.]' in stdout
+    ) == show_verbose_note
+
+
+@pytest.mark.parametrize(
+    'args, expected',
+    [
+        (['--python-version', '3.7'], "(target: version_info='3.7')"),
+    ]
+)
+def test_debug__target_options(script, args, expected):
+    """
+    Check passing target-related options.
+    """
+    args = ['debug'] + args
+    result = script.pip(*args)
+    stdout = result.stdout
+
+    assert 'Compatible tags: ' in stdout
+    assert expected in stdout
diff --git a/tests/unit/test_target_python.py b/tests/unit/test_target_python.py
index 2230b12b7e2..0cca55e13a1 100644
--- a/tests/unit/test_target_python.py
+++ b/tests/unit/test_target_python.py
@@ -47,6 +47,29 @@ def test_init__py_version_info_none(self):
         assert target_python.py_version_info == CURRENT_PY_VERSION_INFO
         assert target_python.py_version == current_major_minor
 
+    @pytest.mark.parametrize('kwargs, expected', [
+        ({}, ''),
+        (dict(py_version_info=(3, 6)), "version_info='3.6'"),
+        (
+            dict(platform='darwin', py_version_info=(3, 6)),
+            "platform='darwin' version_info='3.6'",
+        ),
+        (
+            dict(
+                platform='darwin', py_version_info=(3, 6), abi='cp36m',
+                implementation='cp'
+            ),
+            (
+                "platform='darwin' version_info='3.6' abi='cp36m' "
+                "implementation='cp'"
+            ),
+        ),
+    ])
+    def test_format_given(self, kwargs, expected):
+        target_python = TargetPython(**kwargs)
+        actual = target_python.format_given()
+        assert actual == expected
+
     @pytest.mark.parametrize('py_version_info, expected_versions', [
         ((), ['']),
         ((2, ), ['2']),