Index: ps/trunk/binaries/data/config/default.cfg
===================================================================
--- ps/trunk/binaries/data/config/default.cfg
+++ ps/trunk/binaries/data/config/default.cfg
@@ -284,6 +284,7 @@
 idlewarrior = Slash, NumDivide          ; Select next idle warrior
 idleunit = BackSlash                    ; Select next idle unit
 offscreen = Alt                         ; Include offscreen units in selection
+singleselection = "" ; Select only one entity of a formation.
 [hotkey.selection.group.add]
 0 = "Shift+0", "Shift+Num0"
 1 = "Shift+1", "Shift+Num1"
Index: ps/trunk/binaries/data/mods/public/gui/hotkeys/spec/selection.json
===================================================================
--- ps/trunk/binaries/data/mods/public/gui/hotkeys/spec/selection.json
+++ ps/trunk/binaries/data/mods/public/gui/hotkeys/spec/selection.json
@@ -55,6 +55,10 @@
 				"name": "Include offscreen",
 				"desc": "Include offscreen units in selection."
 			},
+			"selection.singleselection": {
+				"name": "Single selection",
+				"desc": "Select only one entity of a formation."
+			},
 			"selection.group.save.0": {
 				"name": "Set Control Group 0",
 				"desc": "Save current selection as Control Group 0."
Index: ps/trunk/binaries/data/mods/public/gui/session/input.js
===================================================================
--- ps/trunk/binaries/data/mods/public/gui/session/input.js
+++ ps/trunk/binaries/data/mods/public/gui/session/input.js
@@ -1170,7 +1170,7 @@
 		));
 	if (unit)
 	{
-		g_Selection.removeList([unit]);
+		g_Selection.removeList([unit], true);
 		return [unit];
 	}
 	return null;
Index: ps/trunk/binaries/data/mods/public/gui/session/selection.js
===================================================================
--- ps/trunk/binaries/data/mods/public/gui/session/selection.js
+++ ps/trunk/binaries/data/mods/public/gui/session/selection.js
@@ -284,9 +284,9 @@
 	if (firstEntState && firstEntState.player != g_ViewedPlayer && !force)
 		return;
 
-	let added = [];
+	const added = [];
 
-	for (const ent of ents)
+	for (const ent of this.addFormationMembers(ents))
 	{
 		if (this.selected.size >= g_MaxSelectionSize)
 			break;
@@ -324,11 +324,15 @@
 	this.onChange();
 };
 
-EntitySelection.prototype.removeList = function(ents)
+/**
+ * @param {number[]} ents - The entities to remove.
+ * @param {boolean} dontAddFormationMembers - If true we need to exclude adding formation members.
+ */
+EntitySelection.prototype.removeList = function(ents, dontAddFormationMembers = false)
 {
-	var removed = [];
+	const removed = [];
 
-	for (let ent of ents)
+	for (const ent of dontAddFormationMembers ? ents : this.addFormationMembers(ents))
 		if (this.selected.has(ent))
 		{
 			this.groups.removeEnt(ent);
@@ -407,9 +411,10 @@
 	return result;
 };
 
-EntitySelection.prototype.setHighlightList = function(ents)
+EntitySelection.prototype.setHighlightList = function(entities)
 {
 	const highlighted = new Set();
+	const ents = this.addFormationMembers(entities);
 	for (const ent of ents)
 		highlighted.add(ent);
 
@@ -462,6 +467,28 @@
 }
 
 /**
+ * Adds the formation members of a selected entities to the selection.
+ * @param {number[]} entities - The entity IDs of selected entities.
+ * @return {number[]} - Some more entity IDs if part of a formation was selected.
+ */
+EntitySelection.prototype.addFormationMembers = function(entities)
+{
+	if (!entities.length || Engine.HotkeyIsPressed("selection.singleselection"))
+		return entities;
+
+	const result = new Set(entities);
+	for (const entity of entities)
+	{
+		const entState = GetEntityState(+entity);
+		if (entState?.unitAI?.formation)
+			for (const member of GetEntityState(+entState.unitAI.formation).formation.members)
+				result.add(member);
+	}
+
+	return result;
+};
+
+/**
  * Cache some quantities which depends only on selection
  */
 
Index: ps/trunk/binaries/data/mods/public/simulation/components/GuiInterface.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/components/GuiInterface.js
+++ ps/trunk/binaries/data/mods/public/simulation/components/GuiInterface.js
@@ -281,6 +281,12 @@
 			"controllable": cmpIdentity.IsControllable()
 		};
 
+	const cmpFormation = Engine.QueryInterface(ent, IID_Formation);
+	if (cmpFormation)
+		ret.formation = {
+			"members": cmpFormation.GetMembers()
+		};
+
 	let cmpPosition = Engine.QueryInterface(ent, IID_Position);
 	if (cmpPosition && cmpPosition.IsInWorld())
 		ret.position = cmpPosition.GetPosition();
@@ -416,7 +422,8 @@
 			"isGuarding": cmpUnitAI.IsGuardOf(),
 			"canPatrol": cmpUnitAI.CanPatrol(),
 			"selectableStances": cmpUnitAI.GetSelectableStances(),
-			"isIdle": cmpUnitAI.IsIdle()
+			"isIdle": cmpUnitAI.IsIdle(),
+			"formation": cmpUnitAI.GetFormationController()
 		};
 
 	let cmpGuard = Engine.QueryInterface(ent, IID_Guard);
Index: ps/trunk/binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
+++ ps/trunk/binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
@@ -10,6 +10,7 @@
 Engine.LoadComponentScript("interfaces/DeathDamage.js");
 Engine.LoadComponentScript("interfaces/EndGameManager.js");
 Engine.LoadComponentScript("interfaces/EntityLimits.js");
+Engine.LoadComponentScript("interfaces/Formation.js");
 Engine.LoadComponentScript("interfaces/Foundation.js");
 Engine.LoadComponentScript("interfaces/Garrisonable.js");
 Engine.LoadComponentScript("interfaces/GarrisonHolder.js");