diff --git a/doc/admin-guide/logging/formatting.en.rst b/doc/admin-guide/logging/formatting.en.rst
index bbb31501dc4..2d5ab388f4f 100644
--- a/doc/admin-guide/logging/formatting.en.rst
+++ b/doc/admin-guide/logging/formatting.en.rst
@@ -320,6 +320,7 @@ Identifiers
 .. _crid:
 .. _cruuid:
 .. _puuid:
+.. _rcfln:
 
 Logging fields used to obtain various unique identifiers for transactions or
 objects.
@@ -333,6 +334,10 @@ cruuid Client Request UUID of the current client request; generated by
                       concatenating the puuid_ and crid_ field values.
 puuid  Proxy Server   UUID for the currently running :program:`traffic_server`
                       process. Regenerated on every |TS| startup.
+rcfln  Proxy Server   If the client request URL was remapped using a rule from
+                      URL remapping configuration file (specified by
+                      :ts:cv:`proxy.config.url_remap.filename`), the line number of
+                      the rule in the file.  Otherwise, the value is zero.
 ====== ============== =========================================================
 
 .. _admin-logging-fields-lengths:
diff --git a/proxy/http/remap/RemapConfig.cc b/proxy/http/remap/RemapConfig.cc
index 1f889df14b2..39eb5b89600 100644
--- a/proxy/http/remap/RemapConfig.cc
+++ b/proxy/http/remap/RemapConfig.cc
@@ -1161,7 +1161,7 @@ remap_parse_config_bti(const char *path, BUILD_TABLE_INFO *bti)
       goto MAP_ERROR;
     }
 
-    new_mapping = new url_mapping();
+    new_mapping = new url_mapping(cln + 1);
 
     // apply filter rules if we have to
     if ((errStr = process_filter_opt(new_mapping, bti, errStrBuf, sizeof(errStrBuf))) != nullptr) {
@@ -1361,7 +1361,7 @@ remap_parse_config_bti(const char *path, BUILD_TABLE_INFO *bti)
             url_mapping *u_mapping;
 
             ats_ip_ntop(ai_spot->ai_addr, ipb, sizeof ipb);
-            u_mapping = new url_mapping;
+            u_mapping = new url_mapping(cln + 1);
             u_mapping->fromURL.create(nullptr);
             u_mapping->fromURL.copy(&new_mapping->fromURL);
             u_mapping->fromURL.host_set(ipb, strlen(ipb));
diff --git a/proxy/http/remap/UrlMapping.cc b/proxy/http/remap/UrlMapping.cc
index e83d1c85fe1..987c473e6d7 100644
--- a/proxy/http/remap/UrlMapping.cc
+++ b/proxy/http/remap/UrlMapping.cc
@@ -28,7 +28,7 @@
 /**
  *
 **/
-url_mapping::url_mapping()
+url_mapping::url_mapping(int config_file_line_num) : _config_file_line_num(config_file_line_num)
 {
   memset(_plugin_list, 0, sizeof(_plugin_list));
   memset(_instance_data, 0, sizeof(_instance_data));
diff --git a/proxy/http/remap/UrlMapping.h b/proxy/http/remap/UrlMapping.h
index 89d4258fccf..f9f33befb09 100644
--- a/proxy/http/remap/UrlMapping.h
+++ b/proxy/http/remap/UrlMapping.h
@@ -79,7 +79,10 @@ class redirect_tag_str
 class url_mapping
 {
 public:
-  url_mapping();
+  // Constructor parameter is the line number of the remapping from the configured url_remap file.  The value should be zero if
+  // the remapping was not configured in this file.
+  //
+  url_mapping(int config_file_line_num);
   ~url_mapping();
 
   bool add_plugin(remap_plugin_info *i, void *ih);
@@ -122,11 +125,17 @@ class url_mapping
   {
     _rank = rank;
   };
+  int
+  config_file_line_num() const
+  {
+    return _config_file_line_num;
+  }
 
 private:
   remap_plugin_info *_plugin_list[MAX_REMAP_PLUGIN_CHAIN];
   void *_instance_data[MAX_REMAP_PLUGIN_CHAIN];
   int _rank = 0;
+  int _config_file_line_num;
 };
 
 /**
diff --git a/proxy/http/remap/UrlRewrite.cc b/proxy/http/remap/UrlRewrite.cc
index ef35a901861..6f46d467eed 100644
--- a/proxy/http/remap/UrlRewrite.cc
+++ b/proxy/http/remap/UrlRewrite.cc
@@ -144,7 +144,7 @@ UrlRewrite::SetupBackdoorMapping()
   const char from_url[] = "/ink/rh";
   const char to_url[]   = "http://{backdoor}/ink/rh";
 
-  url_mapping *mapping = new url_mapping;
+  url_mapping *mapping = new url_mapping(0);
 
   mapping->fromURL.create(nullptr);
   mapping->fromURL.parse(from_url, sizeof(from_url) - 1);
diff --git a/proxy/logging/Log.cc b/proxy/logging/Log.cc
index 0a2fe4d0a27..528f9103212 100644
--- a/proxy/logging/Log.cc
+++ b/proxy/logging/Log.cc
@@ -484,6 +484,11 @@ Log::init_fields()
   global_field_list.add(field, false);
   ink_hash_table_insert(field_symbol_hash, "puuid", field);
 
+  field = new LogField("remap_config_file_line_number", "rcfln", LogField::sINT, &LogAccess::marshal_url_remap_config_line_num,
+                       &LogAccess::unmarshal_int_to_str);
+  global_field_list.add(field, false);
+  ink_hash_table_insert(field_symbol_hash, "rcfln", field);
+
   // TS-4765: This alias is deprecated to be removed in 8.0.
   field = new LogField("client_req_body_len", "cqbl", LogField::sINT, &LogAccess::marshal_client_req_content_len,
                        &LogAccess::unmarshal_int_to_str);
diff --git a/proxy/logging/LogAccess.cc b/proxy/logging/LogAccess.cc
index 916db70b30a..d652246f34c 100644
--- a/proxy/logging/LogAccess.cc
+++ b/proxy/logging/LogAccess.cc
@@ -498,6 +498,11 @@ LOG_ACCESS_DEFAULT_FIELD(marshal_client_http_connection_id, DEFAULT_INT_FIELD)
 
 LOG_ACCESS_DEFAULT_FIELD(marshal_client_http_transaction_id, DEFAULT_INT_FIELD)
 
+/*-------------------------------------------------------------------------
+  -------------------------------------------------------------------------*/
+
+LOG_ACCESS_DEFAULT_FIELD(marshal_url_remap_config_line_num, DEFAULT_INT_FIELD)
+
 /*-------------------------------------------------------------------------
   -------------------------------------------------------------------------*/
 
diff --git a/proxy/logging/LogAccess.h b/proxy/logging/LogAccess.h
index 47d368bcf9c..75bee95d656 100644
--- a/proxy/logging/LogAccess.h
+++ b/proxy/logging/LogAccess.h
@@ -277,6 +277,7 @@ class LogAccess
   inkcoreapi virtual int marshal_process_uuid(char *);               // STR
   inkcoreapi virtual int marshal_client_http_connection_id(char *);  // INT
   inkcoreapi virtual int marshal_client_http_transaction_id(char *); // INT
+  inkcoreapi virtual int marshal_url_remap_config_line_num(char *);  // INT
 
   // These two are special, in that they are shared for all log types / implementations
   inkcoreapi int marshal_entry_type(char *);                     // INT
diff --git a/proxy/logging/LogAccessHttp.cc b/proxy/logging/LogAccessHttp.cc
index 93e15ce9bc2..4384546490a 100644
--- a/proxy/logging/LogAccessHttp.cc
+++ b/proxy/logging/LogAccessHttp.cc
@@ -1505,6 +1505,25 @@ LogAccessHttp::marshal_client_http_transaction_id(char *buf)
   return INK_MIN_ALIGN;
 }
 
+/*-------------------------------------------------------------------------
+  -------------------------------------------------------------------------*/
+
+int
+LogAccessHttp::marshal_url_remap_config_line_num(char *buf)
+{
+  if (buf) {
+    int64_t line_num = 0;
+    if (m_http_sm) {
+      auto m = m_http_sm->t_state.url_map.getMapping();
+      if (m) {
+        line_num = m->config_file_line_num();
+      }
+    }
+    marshal_int(buf, line_num);
+  }
+  return INK_MIN_ALIGN;
+}
+
 /*-------------------------------------------------------------------------
   -------------------------------------------------------------------------*/
 
diff --git a/proxy/logging/LogAccessHttp.h b/proxy/logging/LogAccessHttp.h
index 0c20ef25a6f..a4f9655b97c 100644
--- a/proxy/logging/LogAccessHttp.h
+++ b/proxy/logging/LogAccessHttp.h
@@ -155,6 +155,7 @@ class LogAccessHttp : public LogAccess
   int marshal_cache_lookup_url_canon(char *) override;     // STR
   int marshal_client_http_connection_id(char *) override;  // INT
   int marshal_client_http_transaction_id(char *) override; // INT
+  int marshal_url_remap_config_line_num(char *) override;  // INT
 
   //
   // named fields from within a http header
diff --git a/tests/gold_tests/logging/gold/test_rcfln.gold b/tests/gold_tests/logging/gold/test_rcfln.gold
new file mode 100644
index 00000000000..56aa836c979
--- /dev/null
+++ b/tests/gold_tests/logging/gold/test_rcfln.gold
@@ -0,0 +1,5 @@
+1
+6
+1
+0
+4
diff --git a/tests/gold_tests/logging/remap_line_num.test.py b/tests/gold_tests/logging/remap_line_num.test.py
new file mode 100644
index 00000000000..fe8ecbb1b93
--- /dev/null
+++ b/tests/gold_tests/logging/remap_line_num.test.py
@@ -0,0 +1,107 @@
+'''
+'''
+#  Licensed to the Apache Software Foundation (ASF) under one
+#  or more contributor license agreements.  See the NOTICE file
+#  distributed with this work for additional information
+#  regarding copyright ownership.  The ASF licenses this file
+#  to you under the Apache License, Version 2.0 (the
+#  "License"); you may not use this file except in compliance
+#  with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+import os
+import subprocess
+
+Test.Summary = '''
+Test new log field giving line number in config file of rule used to remap URL.
+'''
+
+Test.SkipUnless(
+    Condition.HasProgram("curl", "Curl need to be installed on system for this test to work")
+)
+Test.ContinueOnFail = True
+
+ts = Test.MakeATSProcess("ts", select_ports=False)
+
+ts.Disk.records_config.update({
+    # 'proxy.config.diags.debug.enabled': 1,
+    'proxy.config.http.server_ports': 'ipv4:{0}'.format(ts.Variables.port)
+})
+
+ts.Disk.remap_config.AddLine(
+    'map http://127.0.0.1:{0} http://httpbin.org/ip'.format(ts.Variables.port)
+)
+
+ts.Disk.remap_config.AddLine('')
+ts.Disk.remap_config.AddLine('')
+
+ts.Disk.remap_config.AddLine(
+    'map http://127.0.0.3:{0} http://httpbin.org/ip'.format(ts.Variables.port)
+)
+
+ts.Disk.remap_config.AddLine('')
+
+ts.Disk.remap_config.AddLine(
+    'map http://127.0.0.2:{0} http://httpbin.org/ip'.format(ts.Variables.port)
+)
+
+ts.Disk.logging_config.AddLines(
+    '''custom = format {
+  Format = "%<rcfln>"
+}
+
+log.ascii {
+  Format = custom,
+  Filename = 'test_rcfln'
+}'''.split("\n")
+)
+
+Test.Disk.File(os.path.join(ts.Variables.LOGDIR, 'test_rcfln.log'),
+               exists=True, content='gold/test_rcfln.gold')
+
+# Ask the OS if the port is ready for connect()
+#
+def CheckPort(Port):
+    return lambda: 0 == subprocess.call('netstat --listen --tcp -n | grep -q :{}'.format(Port), shell=True)
+
+tr = Test.AddTestRun()
+# Delay on readiness of port
+tr.Processes.Default.StartBefore(Test.Processes.ts, ready=CheckPort(ts.Variables.port))
+#
+tr.Processes.Default.Command = 'curl "http://127.0.0.1:{0}" --verbose'.format(
+    ts.Variables.port)
+tr.Processes.Default.ReturnCode = 0
+
+tr = Test.AddTestRun()
+tr.Processes.Default.Command = 'curl "http://127.0.0.2:{0}" --verbose'.format(
+    ts.Variables.port)
+tr.Processes.Default.ReturnCode = 0
+
+tr = Test.AddTestRun()
+tr.Processes.Default.Command = 'curl "http://127.0.0.1:{0}" --verbose'.format(
+    ts.Variables.port)
+tr.Processes.Default.ReturnCode = 0
+
+# Unremapped URL
+tr = Test.AddTestRun()
+tr.Processes.Default.Command = 'curl "http://127.0.0.4:{0}" --verbose'.format(
+    ts.Variables.port)
+tr.Processes.Default.ReturnCode = 0
+
+tr = Test.AddTestRun()
+tr.Processes.Default.Command = 'curl "http://127.0.0.3:{0}" --verbose'.format(
+    ts.Variables.port)
+tr.Processes.Default.ReturnCode = 0
+
+# Delay to give ATS time to generate log entries.
+tr = Test.AddTestRun()
+tr.Processes.Default.Command = 'echo WAIT'
+tr.DelayStart = 10
+tr.Processes.Default.ReturnCode = 0