diff --git a/CHANGES.rst b/CHANGES.rst
index 057d700df..f3d398354 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -5,6 +5,7 @@ Version 8.2.0
 
 Unreleased
 
+-   Add support for custom ``show_default`` string in prompts. :pr:`460a142`
 -   Drop support for Python 3.7. :pr:`2588`
 -   Use modern packaging metadata with ``pyproject.toml`` instead of ``setup.cfg``.
     :pr:`326`
diff --git a/src/click/core.py b/src/click/core.py
index e783729c7..2d000a822 100644
--- a/src/click/core.py
+++ b/src/click/core.py
@@ -2927,10 +2927,10 @@ def prompt_for_value(self, ctx: Context) -> t.Any:
         if self.is_bool_flag:
             return confirm(self.prompt, default)
 
-        # If show_default is set to True/False, provide this to `prompt` as well. For
-        # non-bool values of `show_default`, we use `prompt`'s default behavior
+        # If show_default is given, provide this to `prompt` as well,
+        # otherwise we use `prompt`'s default behavior
         prompt_kwargs: t.Any = {}
-        if isinstance(self.show_default, bool):
+        if self.show_default is not None:
             prompt_kwargs["show_default"] = self.show_default
 
         return prompt(
diff --git a/src/click/termui.py b/src/click/termui.py
index dcbb22216..4a06be23c 100644
--- a/src/click/termui.py
+++ b/src/click/termui.py
@@ -60,7 +60,7 @@ def hidden_prompt_func(prompt: str) -> str:
 def _build_prompt(
     text: str,
     suffix: str,
-    show_default: bool = False,
+    show_default: bool | str = False,
     default: t.Any | None = None,
     show_choices: bool = True,
     type: ParamType | None = None,
@@ -68,6 +68,8 @@ def _build_prompt(
     prompt = text
     if type is not None and show_choices and isinstance(type, Choice):
         prompt += f" ({', '.join(map(str, type.choices))})"
+    if isinstance(show_default, str):
+        default = f"({show_default})"
     if default is not None and show_default:
         prompt = f"{prompt} [{_format_default(default)}]"
     return f"{prompt}{suffix}"
@@ -88,7 +90,7 @@ def prompt(
     type: ParamType | t.Any | None = None,
     value_proc: t.Callable[[str], t.Any] | None = None,
     prompt_suffix: str = ": ",
-    show_default: bool = True,
+    show_default: bool | str = True,
     err: bool = False,
     show_choices: bool = True,
 ) -> t.Any:
@@ -112,6 +114,8 @@ def prompt(
                        convert a value.
     :param prompt_suffix: a suffix that should be added to the prompt.
     :param show_default: shows or hides the default value in the prompt.
+                         If this value is a string, it shows that string
+                         in parentheses instead of the actual value.
     :param err: if set to true the file defaults to ``stderr`` instead of
                 ``stdout``, the same as with echo.
     :param show_choices: Show or hide choices if the passed type is a Choice.
@@ -119,6 +123,9 @@ def prompt(
                          show_choices is true and text is "Group by" then the
                          prompt will be "Group by (day, week): ".
 
+    .. versionadded:: 8.2
+        ``show_default`` can be a custom string.
+
     .. versionadded:: 8.0
         ``confirmation_prompt`` can be a custom string.
 
diff --git a/tests/test_options.py b/tests/test_options.py
index b7267c182..678184dc5 100644
--- a/tests/test_options.py
+++ b/tests/test_options.py
@@ -856,6 +856,19 @@ def test_show_default_string(runner):
     assert "[default: (unlimited)]" in message
 
 
+def test_string_show_default_shows_custom_string_in_prompt(runner):
+    @click.command()
+    @click.option(
+        "--arg1", show_default="custom", prompt=True, default="my-default-value"
+    )
+    def cmd(arg1):
+        pass
+
+    result = runner.invoke(cmd, input="my-input", standalone_mode=False)
+    assert "(custom)" in result.output
+    assert "my-default-value" not in result.output
+
+
 def test_show_default_with_empty_string(runner):
     """When show_default is True and default is set to an empty string."""
     opt = click.Option(["--limit"], default="", show_default=True)
diff --git a/tests/test_termui.py b/tests/test_termui.py
index ad9d0a66c..04ac99460 100644
--- a/tests/test_termui.py
+++ b/tests/test_termui.py
@@ -485,3 +485,16 @@ def cmd(arg1):
     # is False
     result = runner.invoke(cmd, input="my-input", standalone_mode=False)
     assert "my-default-value" not in result.output
+
+
+def test_string_show_default_shows_custom_string_in_prompt(runner):
+    @click.command()
+    @click.option(
+        "--arg1", show_default="custom", prompt=True, default="my-default-value"
+    )
+    def cmd(arg1):
+        pass
+
+    result = runner.invoke(cmd, input="my-input", standalone_mode=False)
+    assert "(custom)" in result.output
+    assert "my-default-value" not in result.output