Z Plan or Plan Z may refer to:
Military and political plans Hypothesis Z, sometimes called Plan Z, the first Romanian plan for World War I Plan Z, a plan for re-equipment and expansion of the Nazi German Navy ordered by Adolf Hitler in 1939 Operation Z, the Japanese code name for the 1941 Attack on Pearl Harbor in its planning stages Operation Z (1944), the initial Japanese plan for the defense of the Marianas Islands in WWII Z-4 Plan, a proposal to settle the Croatian War of Independence
Other Plan Z (TV series), a 1990s Chilean TV series Plan Z, a major plot element in The SpongeBob SquarePants Movie Z-plan castle, a form of castle design common in England and Scotland
See also Project Z (disambiguation)