diff --git a/NAMESPACE b/NAMESPACE
index becf512278..8f4f9c5856 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -94,6 +94,7 @@ S3method(makeContext,dotstackGrob)
 S3method(merge_element,default)
 S3method(merge_element,element)
 S3method(merge_element,element_blank)
+S3method(merge_element,margin)
 S3method(pattern_alpha,GridPattern)
 S3method(pattern_alpha,GridTilingPattern)
 S3method(pattern_alpha,default)
@@ -494,6 +495,8 @@ export(layer_sf)
 export(lims)
 export(map_data)
 export(margin)
+export(margin_auto)
+export(margin_part)
 export(max_height)
 export(max_width)
 export(mean_cl_boot)
diff --git a/NEWS.md b/NEWS.md
index ebbcf92e02..b0c04550c1 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # ggplot2 (development version)
 
+* Theme margins can have NA-units to inherit from parent elements. The new
+  function `margin_part()` has NA-units as default (@teunbrand, #6115)
+* New `margin_auto()` specification for theme margins.
 * New argument `labs(dictionary)` to label based on variable name rather than 
   based on aesthetic (@teunbrand, #5178)
 * Fixed bug in out-of-bounds binned breaks (@teunbrand, #6054)
diff --git a/R/geom-rug.R b/R/geom-rug.R
index d675474f43..ffc761b91c 100644
--- a/R/geom-rug.R
+++ b/R/geom-rug.R
@@ -45,7 +45,7 @@
 #' p +
 #'   geom_rug(outside = TRUE, sides = "tr") +
 #'   coord_cartesian(clip = "off") +
-#'   theme(plot.margin = margin(1, 1, 1, 1, "cm"))
+#'   theme(plot.margin = margin_auto(1, unit = "cm"))
 #'
 #' # increase the line length and
 #' # expand axis to avoid overplotting
diff --git a/R/legend-draw.R b/R/legend-draw.R
index 0f734f8fea..d08c6c6c93 100644
--- a/R/legend-draw.R
+++ b/R/legend-draw.R
@@ -320,7 +320,7 @@ draw_key_text <- function(data, params, size) {
       fontface   = data$fontface %||% 1,
       fontsize   = (data$size %||% 3.88) * .pt
     ),
-    margin = margin(0.1, 0.1, 0.1, 0.1, unit = "lines"),
+    margin = margin_auto(0.1, unit = "lines"),
     margin_x = TRUE, margin_y = TRUE
   )
   attr(grob, "width")  <- convertWidth(grobWidth(grob),   "cm", valueOnly = TRUE)
diff --git a/R/margins.R b/R/margins.R
index 7104a7d330..61ea1dab43 100644
--- a/R/margins.R
+++ b/R/margins.R
@@ -9,6 +9,18 @@ margin <- function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
   u
 }
 
+#' @rdname element
+#' @export
+margin_part <- function(t = NA, r = NA, b = NA, l = NA, unit = "pt") {
+  margin(t = t, r = r, b = b, l = l, unit = unit)
+}
+
+#' @rdname element
+#' @export
+margin_auto <- function(t = 0, r = t, b = t, l = r, unit = "pt") {
+  margin(t = t, r = r, b = b, l = l, unit)
+}
+
 #' @export
 #' @rdname is_tests
 is.margin <- function(x) inherits(x, "margin")
diff --git a/R/theme-defaults.R b/R/theme-defaults.R
index ac8c5ecb51..e6efd2a783 100644
--- a/R/theme-defaults.R
+++ b/R/theme-defaults.R
@@ -143,7 +143,7 @@ theme_grey <- function(base_size = 11, base_family = "",
     title =              element_text(family = header_family),
 
     spacing = unit(half_line, "pt"),
-    margins = margin(half_line, half_line, half_line, half_line),
+    margins = margin_auto(half_line),
 
     geom =               element_geom(
                            ink = ink, paper = paper, accent = "#3366FF",
@@ -226,7 +226,7 @@ theme_grey <- function(base_size = 11, base_family = "",
     strip.text =         element_text(
                            colour = col_mix(ink, paper, 0.105),
                            size = rel(0.8),
-                           margin = margin(0.8 * half_line, 0.8 * half_line, 0.8 * half_line, 0.8 * half_line)
+                           margin = margin_auto(0.8 * half_line)
                          ),
     strip.text.x =       NULL,
     strip.text.y =       element_text(angle = -90),
@@ -341,7 +341,7 @@ theme_linedraw <- function(base_size = 11, base_family = "",
       strip.text       = element_text(
                            colour = paper,
                            size = rel(0.8),
-                           margin = margin(0.8 * half_line, 0.8 * half_line, 0.8 * half_line, 0.8 * half_line)
+                           margin = margin_auto(0.8 * half_line)
                          ),
 
       complete = TRUE
@@ -384,7 +384,7 @@ theme_light <- function(base_size = 11, base_family = "",
       strip.text       = element_text(
                            colour = paper,
                            size = rel(0.8),
-                           margin = margin(0.8 * half_line, 0.8 * half_line, 0.8 * half_line, 0.8 * half_line)
+                           margin = margin_auto(0.8 * half_line)
                          ),
 
       complete = TRUE
@@ -427,7 +427,7 @@ theme_dark <- function(base_size = 11, base_family = "",
       strip.text       = element_text(
                            colour = col_mix(ink, paper, 0.9),
                            size = rel(0.8),
-                           margin = margin(0.8 * half_line, 0.8 * half_line, 0.8 * half_line, 0.8 * half_line)
+                           margin = margin_auto(0.8 * half_line)
                          ),
 
       complete = TRUE
@@ -557,7 +557,7 @@ theme_void <- function(base_size = 11, base_family = "",
                          ),
     title =              element_text(family = header_family),
     spacing =            unit(half_line, "pt"),
-    margins =            margin(half_line, half_line, half_line, half_line),
+    margins =            margin_auto(half_line),
     axis.text =          element_blank(),
     axis.title =         element_blank(),
     axis.ticks.length =  rel(0),
@@ -641,7 +641,7 @@ theme_test <- function(base_size = 11, base_family = "",
                          ),
     title =              element_text(family = header_family),
     spacing = unit(half_line, "pt"),
-    margins = margin(half_line, half_line, half_line, half_line),
+    margins = margin_auto(half_line),
     geom =               element_geom(
                            ink = ink, paper = paper, accent = "#3366FF",
                            linewidth = base_line_size, borderwidth = base_line_size,
@@ -690,7 +690,7 @@ theme_test <- function(base_size = 11, base_family = "",
     legend.spacing =     rel(2),
     legend.spacing.x =   NULL,
     legend.spacing.y =   NULL,
-    legend.margin =      margin(0, 0, 0, 0, "cm"),
+    legend.margin =      margin_auto(0, unit = "cm"),
     legend.key =         NULL,
     legend.key.size =    unit(1.2, "lines"),
     legend.key.height =  NULL,
@@ -705,7 +705,7 @@ theme_test <- function(base_size = 11, base_family = "",
     legend.direction =   NULL,
     legend.justification = "center",
     legend.box =         NULL,
-    legend.box.margin =  margin(0, 0, 0, 0, "cm"),
+    legend.box.margin =  margin_auto(0, unit = "cm"),
     legend.box.background = element_blank(),
     legend.box.spacing = rel(2),
 
@@ -726,7 +726,7 @@ theme_test <- function(base_size = 11, base_family = "",
     strip.text =         element_text(
                            colour = col_mix(ink, paper, 0.105),
                            size = rel(0.8),
-                           margin = margin(0.8 * half_line, 0.8 * half_line, 0.8 * half_line, 0.8 * half_line)
+                           margin = margin_auto(0.8 * half_line)
                          ),
     strip.text.x =       NULL,
     strip.text.y =       element_text(angle = -90),
diff --git a/R/theme-elements.R b/R/theme-elements.R
index c51134216f..b1cb67b046 100644
--- a/R/theme-elements.R
+++ b/R/theme-elements.R
@@ -11,7 +11,8 @@
 #'   - `element_geom()`: defaults for drawing layers.
 #'
 #' `rel()` is used to specify sizes relative to the parent,
-#' `margin()` is used to specify the margins of elements.
+#' `margin()`, `margin_part()` and `margin_auto()` are all used to specify the
+#' margins of elements.
 #'
 #' @param fill Fill colour.
 #' @param colour,color Line/border colour. Color is an alias for colour.
@@ -42,7 +43,7 @@
 #'
 #' plot + theme(
 #'   panel.background = element_rect(fill = "white"),
-#'   plot.margin = margin(2, 2, 2, 2, "cm"),
+#'   plot.margin = margin_auto(2, unit = "cm"),
 #'   plot.background = element_rect(
 #'     fill = "grey90",
 #'     colour = "black",
diff --git a/R/theme.R b/R/theme.R
index 2eecc13253..04ab2edf98 100644
--- a/R/theme.R
+++ b/R/theme.R
@@ -281,14 +281,14 @@
 #'   legend.position.inside = c(.95, .95),
 #'   legend.justification = c("right", "top"),
 #'   legend.box.just = "right",
-#'   legend.margin = margin(6, 6, 6, 6)
+#'   legend.margin = margin_auto(6)
 #' )
 #'
 #' # The legend.box properties work similarly for the space around
 #' # all the legends
 #' p2 + theme(
 #'   legend.box.background = element_rect(),
-#'   legend.box.margin = margin(6, 6, 6, 6)
+#'   legend.box.margin = margin_auto(6)
 #' )
 #'
 #' # You can also control the display of the keys
@@ -835,6 +835,18 @@ merge_element.element <- function(new, old) {
   new
 }
 
+#' @rdname merge_element
+#' @export
+merge_element.margin <- function(new, old) {
+  if (is.null(old) || inherits(old, "element_blank")) {
+    return(new)
+  }
+  if (anyNA(new)) {
+    new[is.na(new)] <- old[is.na(new)]
+  }
+  new
+}
+
 #' Combine the properties of two elements
 #'
 #' @param e1 An element object
@@ -868,6 +880,15 @@ combine_elements <- function(e1, e2) {
     return(e1)
   }
 
+  if (inherits(e1, "margin") && inherits(e2, "margin")) {
+    if (anyNA(e2)) {
+      e2[is.na(e2)] <- unit(0, "pt")
+    }
+    if (anyNA(e1)) {
+      e1[is.na(e1)] <- e2[is.na(e1)]
+    }
+  }
+
   # If neither of e1 or e2 are element_* objects, return e1
   if (!inherits(e1, "element") && !inherits(e2, "element")) {
     return(e1)
@@ -897,6 +918,10 @@ combine_elements <- function(e1, e2) {
     e1$linewidth <- e2$linewidth * unclass(e1$linewidth)
   }
 
+  if (inherits(e1, "element_text")) {
+    e1$margin <- combine_elements(e1$margin, e2$margin)
+  }
+
   # If e2 is 'richer' than e1, fill e2 with e1 parameters
   is_subclass <- !any(inherits(e2, class(e1), which = TRUE) == 0)
   is_subclass <- is_subclass && length(setdiff(class(e2), class(e1)) > 0)
diff --git a/man/element.Rd b/man/element.Rd
index adb1b7eb22..c43fadfed2 100644
--- a/man/element.Rd
+++ b/man/element.Rd
@@ -8,6 +8,8 @@
 \alias{element_geom}
 \alias{rel}
 \alias{margin}
+\alias{margin_part}
+\alias{margin_auto}
 \title{Theme elements}
 \usage{
 element_blank()
@@ -66,6 +68,10 @@ element_geom(
 rel(x)
 
 margin(t = 0, r = 0, b = 0, l = 0, unit = "pt")
+
+margin_part(t = NA, r = NA, b = NA, l = NA, unit = "pt")
+
+margin_auto(t = 0, r = t, b = t, l = r, unit = "pt")
 }
 \arguments{
 \item{fill}{Fill colour.}
@@ -145,7 +151,8 @@ specify the display of how non-data components of the plot are drawn.
 }
 
 \code{rel()} is used to specify sizes relative to the parent,
-\code{margin()} is used to specify the margins of elements.
+\code{margin()}, \code{margin_part()} and \code{margin_auto()} are all used to specify the
+margins of elements.
 }
 \examples{
 plot <- ggplot(mpg, aes(displ, hwy)) + geom_point()
@@ -165,7 +172,7 @@ plot + theme(
 
 plot + theme(
   panel.background = element_rect(fill = "white"),
-  plot.margin = margin(2, 2, 2, 2, "cm"),
+  plot.margin = margin_auto(2, unit = "cm"),
   plot.background = element_rect(
     fill = "grey90",
     colour = "black",
diff --git a/man/geom_rug.Rd b/man/geom_rug.Rd
index 1cc10e785a..b6508c7f9a 100644
--- a/man/geom_rug.Rd
+++ b/man/geom_rug.Rd
@@ -170,7 +170,7 @@ p +
 p +
   geom_rug(outside = TRUE, sides = "tr") +
   coord_cartesian(clip = "off") +
-  theme(plot.margin = margin(1, 1, 1, 1, "cm"))
+  theme(plot.margin = margin_auto(1, unit = "cm"))
 
 # increase the line length and
 # expand axis to avoid overplotting
diff --git a/man/merge_element.Rd b/man/merge_element.Rd
index 4071e6c69a..ca993eeec3 100644
--- a/man/merge_element.Rd
+++ b/man/merge_element.Rd
@@ -5,6 +5,7 @@
 \alias{merge_element.default}
 \alias{merge_element.element_blank}
 \alias{merge_element.element}
+\alias{merge_element.margin}
 \title{Merge a parent element into a child element}
 \usage{
 merge_element(new, old)
@@ -14,6 +15,8 @@ merge_element(new, old)
 \method{merge_element}{element_blank}(new, old)
 
 \method{merge_element}{element}(new, old)
+
+\method{merge_element}{margin}(new, old)
 }
 \arguments{
 \item{new}{The child element in the theme hierarchy}
diff --git a/man/theme.Rd b/man/theme.Rd
index 829254ecdf..869e45ea71 100644
--- a/man/theme.Rd
+++ b/man/theme.Rd
@@ -469,14 +469,14 @@ p2 + theme(
   legend.position.inside = c(.95, .95),
   legend.justification = c("right", "top"),
   legend.box.just = "right",
-  legend.margin = margin(6, 6, 6, 6)
+  legend.margin = margin_auto(6)
 )
 
 # The legend.box properties work similarly for the space around
 # all the legends
 p2 + theme(
   legend.box.background = element_rect(),
-  legend.box.margin = margin(6, 6, 6, 6)
+  legend.box.margin = margin_auto(6)
 )
 
 # You can also control the display of the keys
diff --git a/tests/testthat/test-theme.R b/tests/testthat/test-theme.R
index 2f7f7874f9..a1b656dbab 100644
--- a/tests/testthat/test-theme.R
+++ b/tests/testthat/test-theme.R
@@ -617,6 +617,22 @@ test_that("complete_theme completes a theme", {
   reset_theme_settings()
 })
 
+test_that("margin_part() mechanics work as expected", {
+
+  t <- theme_gray() +
+    theme(plot.margin = margin_part(b = 11))
+
+  test <- calc_element("plot.margin", t)
+  expect_equal(as.numeric(test), c(5.5, 5.5, 11, 5.5))
+
+  t <- theme_gray() +
+    theme(margins = margin_part(b = 11))
+
+  test <- calc_element("plot.margin", t)
+  expect_equal(as.numeric(test), c(5.5, 5.5, 11, 5.5))
+
+})
+
 # Visual tests ------------------------------------------------------------
 
 test_that("aspect ratio is honored", {