diff --git a/NEWS.md b/NEWS.md
index 9f20de2a2e..c8814884a4 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -73,6 +73,8 @@
   therefore stacking is not necessary (#5788).
 * A new `ggplot_build()` S3 method for <ggplot_built> classes was added, which
   returns input unaltered (@teunbrand, #5800).
+* `width` is implemented as aesthetic instead of parameter in `geom_col()` and
+  `geom_bar()` (#3142).
 
 # ggplot2 3.5.1
 
diff --git a/R/geom-bar.R b/R/geom-bar.R
index e4611fbabb..de7490bfc4 100644
--- a/R/geom-bar.R
+++ b/R/geom-bar.R
@@ -45,8 +45,6 @@
 #'   columns to the left/right of axis breaks. Note that this argument may have
 #'   unintended behaviour when used with alternative positions, e.g.
 #'   `position_dodge()`.
-#' @param width Bar width. By default, set to 90% of the [resolution()] of the
-#'   data.
 #' @param geom,stat Override the default connection between `geom_bar()` and
 #'   `stat_count()`. For more information about overriding these connections,
 #'   see how the [stat][layer_stats] and [geom][layer_geoms] arguments work.
@@ -98,7 +96,6 @@ geom_bar <- function(mapping = NULL, data = NULL,
                      stat = "count", position = "stack",
                      ...,
                      just = 0.5,
-                     width = NULL,
                      na.rm = FALSE,
                      orientation = NA,
                      show.legend = NA,
@@ -113,7 +110,6 @@ geom_bar <- function(mapping = NULL, data = NULL,
     inherit.aes = inherit.aes,
     params = list2(
       just = just,
-      width = width,
       na.rm = na.rm,
       orientation = orientation,
       ...
@@ -134,6 +130,8 @@ GeomBar <- ggproto("GeomBar", GeomRect,
   # limits, not just those for which x and y are outside the limits
   non_missing_aes = c("xmin", "xmax", "ymin", "ymax"),
 
+  default_aes = aes(!!!GeomRect$default_aes, width = NULL),
+
   setup_params = function(data, params) {
     params$flipped_aes <- has_flipped_aes(data, params)
     params
@@ -158,16 +156,5 @@ GeomBar <- ggproto("GeomBar", GeomRect,
     flip_data(data, params$flipped_aes)
   },
 
-  draw_panel = function(self, data, panel_params, coord, lineend = "butt",
-                        linejoin = "mitre", width = NULL, flipped_aes = FALSE) {
-    # Hack to ensure that width is detected as a parameter
-    ggproto_parent(GeomRect, self)$draw_panel(
-      data,
-      panel_params,
-      coord,
-      lineend = lineend,
-      linejoin = linejoin
-    )
-  },
   rename_size = TRUE
 )
diff --git a/R/geom-col.R b/R/geom-col.R
index 2dc07f12da..77c756f573 100644
--- a/R/geom-col.R
+++ b/R/geom-col.R
@@ -4,7 +4,6 @@ geom_col <- function(mapping = NULL, data = NULL,
                      position = "stack",
                      ...,
                      just = 0.5,
-                     width = NULL,
                      na.rm = FALSE,
                      show.legend = NA,
                      inherit.aes = TRUE) {
@@ -19,7 +18,6 @@ geom_col <- function(mapping = NULL, data = NULL,
     inherit.aes = inherit.aes,
     params = list2(
       just = just,
-      width = width,
       na.rm = na.rm,
       ...
     )
diff --git a/R/stat-count.R b/R/stat-count.R
index 18dc1ebaa6..fd78d1beaa 100644
--- a/R/stat-count.R
+++ b/R/stat-count.R
@@ -13,7 +13,6 @@
 stat_count <- function(mapping = NULL, data = NULL,
                        geom = "bar", position = "stack",
                        ...,
-                       width = NULL,
                        na.rm = FALSE,
                        orientation = NA,
                        show.legend = NA,
@@ -22,7 +21,6 @@ stat_count <- function(mapping = NULL, data = NULL,
   params <- list2(
     na.rm = na.rm,
     orientation = orientation,
-    width = width,
     ...
   )
 
diff --git a/man/geom_bar.Rd b/man/geom_bar.Rd
index a974f9824e..4f8196b4c1 100644
--- a/man/geom_bar.Rd
+++ b/man/geom_bar.Rd
@@ -13,7 +13,6 @@ geom_bar(
   position = "stack",
   ...,
   just = 0.5,
-  width = NULL,
   na.rm = FALSE,
   orientation = NA,
   show.legend = NA,
@@ -26,7 +25,6 @@ geom_col(
   position = "stack",
   ...,
   just = 0.5,
-  width = NULL,
   na.rm = FALSE,
   show.legend = NA,
   inherit.aes = TRUE
@@ -38,7 +36,6 @@ stat_count(
   geom = "bar",
   position = "stack",
   ...,
-  width = NULL,
   na.rm = FALSE,
   orientation = NA,
   show.legend = NA,
@@ -113,9 +110,6 @@ columns to the left/right of axis breaks. Note that this argument may have
 unintended behaviour when used with alternative positions, e.g.
 \code{position_dodge()}.}
 
-\item{width}{Bar width. By default, set to 90\% of the \code{\link[=resolution]{resolution()}} of the
-data.}
-
 \item{na.rm}{If \code{FALSE}, the default, missing values are removed with
 a warning. If \code{TRUE}, missing values are silently removed.}
 
@@ -182,6 +176,7 @@ This geom treats each axis differently and, thus, can thus have two orientations
 \item \code{\link[=aes_group_order]{group}}
 \item \code{\link[=aes_linetype_size_shape]{linetype}}
 \item \code{\link[=aes_linetype_size_shape]{linewidth}}
+\item \code{width}
 }
 Learn more about setting these aesthetics in \code{vignette("ggplot2-specs")}.
 
@@ -196,6 +191,7 @@ Learn more about setting these aesthetics in \code{vignette("ggplot2-specs")}.
 \item \code{\link[=aes_group_order]{group}}
 \item \code{\link[=aes_linetype_size_shape]{linetype}}
 \item \code{\link[=aes_linetype_size_shape]{linewidth}}
+\item \code{width}
 }
 Learn more about setting these aesthetics in \code{vignette("ggplot2-specs")}.