The 3rd Motor Brigade was a formation of the Australian Army during the interwar years and early part of World War II.

During World War II, the brigade was mobilised for defensive duties in December 1941 to defend against a possible invasion.

[1] These regiments were based in Benalla, Warragul and Seymour, occupying part of the area previously assigned to the disbanded 5th and 6th Light Horse Brigades.

[2] By 1938, the brigade had been expanded to include the 4/19th, 8th, 13th, 20th and 17th (MG) Light Horse Regiments, and formed part of the 2nd Australian Cavalry Division.

Concentrating around Winchelsea, the brigade's constituent units were deployed to defend possible approaches to Geelong to respond in the event of an invasion.

After training to prepare for combined operations, the brigade came under direct command of III Corps from April 1944, when the 2nd Infantry Division was broken up and ceased to exist.