He was born in Helmscherode, Germany, the son of the landowner Carl Keitel. He was a career soldier, after education in Goettingen he became a Fahnenjunker (Cadet Officer) and joined a artillery regiment. He married in 1909.
During World War I he served on the Western front, becoming a member of the General Staff in 1915. He was seriously wounded in 1917 in Flanders but recovered to join the post-war Freikorps and then returned to the army. He was an instructor for some years before assuming the command of an artillery regiment. In 1929 he joined the Organizations Department.
He was appointed to the Reichswehrministerium (Reich Ministry of War) in 1930, a post he retained after the Nazi seizure of power (1933), as head of the Wehrmachtamt. In 1937 he was made a general and in 1938 after the Blomberg Affair and the replacement of the Reichswehrministerium with the Oberkommando der Wehrmacht (OKW, High Command of the Army) he became Chief of the Supreme Command of the Armed Forces. He was made a Generalfeldmarschall (field marshal) in 1940.
During World War II Keitel proved a weak and cautious commander: he advised Hitler against invading France and opposed Operation Barbarossa. Both times he backed down in the face of Hitler and tendered his resignation: it was not accepted. In 1942 he again stood up to Hitler over Field Marshal Siegmund List. Despite this he was a loyal Nazi, he signed the orders instructing the execution of Jews and Communists and allowed Himmler a free hand with his racial controls in captured Russian territory. His defence of List was his last act of defiance to Hitler, after that he did not challenge another of Hitler's orders and was referred to by his colleagues as Lakaitel. Keitel was instrumental in foiling the attempted coup of the July 20 Plot in 1944, and sat on the following Army Court of Honour that handed many officers over to Roland Freisler's court.
He signed the surrender to the Red Army on May 9, 1945 and was arrested on the 13th. He faced the International Military Tribunal charged with: Conspiracy to commit crimes against peace, planning, initiating and waging wars of aggression, war-crimes and crimes against humanity. His defence that he was just following orders was rejected, he was found guilty on all charges and hanged.