diff --git a/internal/config/config.go b/internal/config/config.go
index d4ded89..d25830e 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -96,8 +96,11 @@ type (
 	}
 
 	SidebarConfig struct {
-		Markers SidebarMarkersConfig `toml:"markers"`
-		Indents SidebarIndentsConfig `toml:"indents"`
+		// WidthPercent is the percentage (%) of the total
+		// window width that the guilds tree sidebar occupies
+		WidthPercent   int                  `toml:"width_percent"`
+		Markers        SidebarMarkersConfig `toml:"markers"`
+		Indents        SidebarIndentsConfig `toml:"indents"`
 	}
 
 	Config struct {
@@ -182,6 +185,14 @@ func applyDefaults(cfg *Config) {
 		cfg.Composer.MaxHeight = 10
 	}
 
+	if cfg.Sidebar.WidthPercent <= 0 || cfg.Sidebar.WidthPercent >= 100 {
+		// these guidelines are simply to guarantee functionality;
+		// there's no guarantee that there's functional utility in
+		// setting an extremely low width, but that's for the
+		// user to decide.
+		cfg.Sidebar.WidthPercent = 20
+	}
+
 	if cfg.DateSeparator.Format == "" {
 		cfg.DateSeparator.Format = "January 2, 2006"
 	}
diff --git a/internal/config/config.toml b/internal/config/config.toml
index 159e28d..0b837c6 100644
--- a/internal/config/config.toml
+++ b/internal/config/config.toml
@@ -68,6 +68,11 @@ send = true
 # Whether to receive typing status or not.
 receive = true
 
+[sidebar]
+# Percentage (%) of the available width used by the guilds tree sidebar.
+# Valid values are 1-99. Invalid values fall back to 20.
+width_percent = 20
+
 [sidebar.markers]
 expanded = "▾ "
 collapsed = "▸ "
diff --git a/internal/ui/chat/model.go b/internal/ui/chat/model.go
index d193da3..41fe91b 100644
--- a/internal/ui/chat/model.go
+++ b/internal/ui/chat/model.go
@@ -138,8 +138,8 @@ func (m *Model) buildLayout() {
 		AddItem(m.composer, 3, 1, false)
 	// The guilds tree is always focused first at start-up.
 	m.mainFlex.
-		AddItem(m.guildsTree, 0, 1, true).
-		AddItem(m.rightFlex, 0, 4, false)
+		AddItem(m.guildsTree, 0, m.cfg.Sidebar.WidthPercent, true).
+		AddItem(m.rightFlex, 0, 100-m.cfg.Sidebar.WidthPercent, false)
 
 	m.AddLayer(m.mainFlex, layers.WithName(flexLayerName), layers.WithResize(true), layers.WithVisible(true))
 	m.AddLayer(