Maximilian Josef Franz Xaver Jais (4 March 1891 – 24 January 1957)was a German military officer who served as a Generalmajor in the Wehrmacht during World War II. A career soldier, he fought on the Western Front in World War I before serving in the invasion of Crete, the northern Eastern Front on the Kola Peninsula, and the final defence of the Westwall in 1944–1945.

Jais was born in Munich, Kingdom of Bavaria, on 4 March 1891. He entered military service on 1 October 1912 as a one-year volunteer (Einjährig-Freiwilliger) in the 7th Bavarian Field Artillery Regiment. After completing his volunteer year, he was discharged to the reserve.

With the outbreak of World War I, Jais was mobilised and served with artillery units on the Western Front. He was commissioned as Leutnant der Reserve on 15 February 1915 and promoted to Oberleutnant der Reserve on 15 March 1918. During the war, he was awarded both classes of the Iron Cross (1914) and the Wound Badge in Black.

Following the armistice, Jais was discharged on 3 January 1919 but was reactivated in the newly formed Reichswehr on 5 May 1919 with the rank of Oberleutnant. He continued his military career during the Weimar Republic, being promoted to Hauptmann on 1 February 1927 and Major on 1 September 1934. With the expansion of the Wehrmacht under the Nazi regime, he was promoted to Oberstleutnant on 1 March 1937.

At the outbreak of World War II in September 1939, Jais was assigned to the staff of Military District Command XVIII (Salzburg). From January to June 1940, he served as Commander of the High Mountain Firing School (Hochgebirgs-Schießschule) in Salzburg.

In mid-1940, Jais received his promotion to Oberst (1 March 1940) and held a succession of regimental commands: the 104th Rifle Regiment (June–December 1940) and the 331st Infantry Regiment (December 1940 – April 1941). On 8 April 1941, he was appointed commander of Gebirgsjäger-Regiment 141, part of the 6th Mountain Division.

For the forthcoming invasion of Crete, Gebirgsjäger-Regiment 141 was detached from the 6th Mountain Division and attached to the 5th Mountain Division under Generalmajor Julius Ringel. Operation Mercury, launched on 20 May 1941, was the first predominantly airborne invasion in military history, with Fallschirmjäger parachute and glider troops attempting to seize the island's airfields against determined Allied and Greek defenders.

After the paratroopers suffered severe casualties on the first day and Maleme airfield was secured on the second, mountain troops including Jais's regiment were airlifted in as reinforcements. By 25 May, elements of the regiment had been committed to the fighting around the Galatas position. On 27 May, the regiment advanced along the coast road east of Chania, where its I Battalion was engaged in fierce close-quarters combat by the New Zealand 28th (Māori) Battalion in an action known as the Battle of 42nd Street. Ringel subsequently ordered the 85th and 141st Mountain Regiments to push eastward toward Souda Bay, driving the Allied forces into retreat toward the south coast evacuation points.