HMAS Steady Hour (12) was a channel patrol boat of the Naval Auxiliary Patrol of the Royal Australian Navy (RAN) during the Second World War. During the 31 May 1942 Japanese attack on Sydney Harbour, Steady Hour deployed 17 depth charges against the Japanese midget submarine M-21 in Taylor's Bay. The submarine's two crew members destroyed their vessel with demolition charges and committed suicide. Steady Hour was awarded the battle honour "Pacific 1942".