diff --git a/bin/blob-theme-gtk b/bin/blob-theme-gtk
new file mode 100755
index 0000000..4a271d4
--- /dev/null
+++ b/bin/blob-theme-gtk
@@ -0,0 +1,22 @@
+#!/bin/bash
+
+# blob:summary=Apply the current Blob theme's light or dark preference to GTK apps
+# blob:hidden=true
+
+blob-cmd-present gsettings || exit 0
+
+colors_toml=$HOME/.local/state/blob/current/theme/colors.toml
+[[ -f $colors_toml ]] || exit 0
+
+mode=$(blob-theme-color --file "$colors_toml" mode)
+
+if [[ $mode == "light" ]]; then
+  color_scheme="prefer-light"
+  gtk_theme="Adwaita"
+else
+  color_scheme="prefer-dark"
+  gtk_theme="Adwaita-dark"
+fi
+
+gsettings set org.gnome.desktop.interface color-scheme "$color_scheme" 2>/dev/null || true
+gsettings set org.gnome.desktop.interface gtk-theme "$gtk_theme" 2>/dev/null || true
diff --git a/bin/blob-theme-set b/bin/blob-theme-set
index f5eb5da..f53f933 100755
--- a/bin/blob-theme-set
+++ b/bin/blob-theme-set
@@ -321,6 +321,7 @@ post_theme_commands=(
   blob-restart-btop
   blob-theme-foot
   blob-theme-browser
+  blob-theme-gtk
 )
 
 if [[ $THEME_HEADLESS != "1" ]]; then
diff --git a/default/themed/gtk.css.tpl b/default/themed/gtk.css.tpl
new file mode 100644
index 0000000..bfde6bf
--- /dev/null
+++ b/default/themed/gtk.css.tpl
@@ -0,0 +1,41 @@
+@define-color window_bg_color {{ background }};
+@define-color window_fg_color {{ foreground }};
+@define-color view_bg_color {{ background }};
+@define-color view_fg_color {{ foreground }};
+@define-color headerbar_bg_color {{ lighter_background }};
+@define-color headerbar_fg_color {{ foreground }};
+@define-color headerbar_border_color {{ dark_background }};
+@define-color headerbar_backdrop_color {{ background }};
+@define-color sidebar_bg_color {{ lighter_background }};
+@define-color sidebar_fg_color {{ foreground }};
+@define-color sidebar_backdrop_color {{ background }};
+@define-color sidebar_border_color {{ dark_background }};
+@define-color secondary_sidebar_bg_color {{ lighter_background }};
+@define-color secondary_sidebar_fg_color {{ foreground }};
+@define-color secondary_sidebar_backdrop_color {{ background }};
+@define-color secondary_sidebar_border_color {{ dark_background }};
+@define-color card_bg_color {{ lighter_background }};
+@define-color card_fg_color {{ foreground }};
+@define-color dialog_bg_color {{ background }};
+@define-color dialog_fg_color {{ foreground }};
+@define-color popover_bg_color {{ lighter_background }};
+@define-color popover_fg_color {{ foreground }};
+@define-color accent_bg_color {{ accent }};
+@define-color accent_fg_color {{ background }};
+@define-color accent_color {{ accent }};
+@define-color destructive_bg_color {{ red }};
+@define-color destructive_fg_color {{ background }};
+@define-color destructive_color {{ red }};
+@define-color success_color {{ green }};
+@define-color warning_color {{ yellow }};
+@define-color error_color {{ red }};
+
+@define-color theme_bg_color {{ background }};
+@define-color theme_fg_color {{ foreground }};
+@define-color theme_base_color {{ background }};
+@define-color theme_text_color {{ foreground }};
+@define-color theme_selected_bg_color {{ accent }};
+@define-color theme_selected_fg_color {{ background }};
+@define-color insensitive_bg_color {{ dark_background }};
+@define-color insensitive_fg_color {{ muted }};
+@define-color borders {{ dark_background }};
diff --git a/docs/themes.md b/docs/themes.md
index 1d91379..bc1da8a 100644
--- a/docs/themes.md
+++ b/docs/themes.md
@@ -30,12 +30,12 @@ the shell and the CLI never disagree about what a slot means.
 Each rendered file is picked up differently: `foot.ini` and `kitty.conf` by an
 `include` in the shipped terminal config, `hyprland.lua` through Hyprland's Lua
 module path, `shell.toml` and `chromium.theme` read straight from the state
-directory, and `btop.theme` and `neovim.lua` through symlinks the installer
-makes into those apps' own config trees.
+directory, and `btop.theme`, `neovim.lua` and `gtk.css` through symlinks the
+installer makes into those apps' own config trees.
 
 `default/themed/*.tpl` are rendered per theme into
-`~/.local/state/blob/current/theme/`. Nine ship: foot, kitty, btop, chromium,
-hyprland, the screenshare picker, neovim, `shell.toml`, and zen.
+`~/.local/state/blob/current/theme/`. Ten ship: foot, kitty, btop, chromium,
+hyprland, the screenshare picker, neovim, `shell.toml`, zen, and `gtk.css`.
 
 An app picks its colors up in one of two ways. Most include the generated file
 directly, so nothing has to run:
@@ -47,7 +47,20 @@ include ~/.local/state/blob/current/theme/kitty.conf
 Zen does the same through a CSS import in `userChrome.css`. The rest are pushed
 by a short applier listed in `post_theme_commands` inside `blob-theme-set`:
 `blob-theme-foot`, `blob-theme-browser`, `blob-restart-terminal`,
-`blob-restart-btop`, `blob-hypr-restart`.
+`blob-restart-btop`, `blob-hypr-restart`, `blob-theme-gtk`.
+
+## GTK apps
+
+Nautilus and the other GTK apps read two things. The palette comes from
+`gtk.css`, linked into both `~/.config/gtk-3.0/gtk.css` and
+`~/.config/gtk-4.0/gtk.css`, which redefines the libadwaita named colors
+(`window_bg_color`, `headerbar_bg_color`, `accent_bg_color` and the rest) so a
+stock Adwaita app is drawn in the theme's own colors. The light or dark
+preference comes from `blob-theme-gtk`, which reads the theme's `mode` and sets
+`org.gnome.desktop.interface color-scheme` and `gtk-theme` through `gsettings`.
+
+The preference applies to running apps immediately; the CSS is read at startup,
+so an app that was already open keeps its old colors until it is restarted.
 
 Adding a template for another app means dropping a `.tpl` in `default/themed/`
 and, if it cannot include a file, adding an applier to that list.
diff --git a/install/steps/theme.sh b/install/steps/theme.sh
index 40e1baf..4a1f4dc 100644
--- a/install/steps/theme.sh
+++ b/install/steps/theme.sh
@@ -131,6 +131,8 @@ link_theme_file() {
 # creating the tree would be inventing a layout the user has not chosen.
 link_app_themes() {
   link_theme_file btop.theme "$config_dir/btop/themes/current.theme" "btop theme"
+  link_theme_file gtk.css "$config_dir/gtk-3.0/gtk.css" "gtk-3.0 theme"
+  link_theme_file gtk.css "$config_dir/gtk-4.0/gtk.css" "gtk-4.0 theme"
 
   if [[ -d $config_dir/nvim/lua/plugins ]]; then
     link_theme_file neovim.lua "$config_dir/nvim/lua/plugins/theme.lua" "neovim theme"
diff --git a/uninstall.sh b/uninstall.sh
index e11799d..66e924a 100755
--- a/uninstall.sh
+++ b/uninstall.sh
@@ -112,6 +112,10 @@ for lua in hyprland.lua monitors.lua input.lua looknfeel.lua bindings.lua autost
   restore_or_remove "$config_dir/hypr/$lua" "hypr/$lua"
 done
 
+for gtk in gtk-3.0 gtk-4.0; do
+  [[ -L $config_dir/$gtk/gtk.css ]] && restore_or_remove "$config_dir/$gtk/gtk.css" "$gtk/gtk.css"
+done
+
 if [[ $keep_state == false && -d $HOME/.local/state/blob ]]; then
   rm -rf "$HOME/.local/state/blob"
   say "remove  ~/.local/state/blob"