Portal:Australia/Anniversaries/May/May 31
- 1813 – Gregory Blaxland, William Lawson, and William Wentworth arrive at Mount Blaxland, and having successfully crossed the Blue Mountains for the first time, head back to Sydney.
- 1886 – The SS Ly-Ee-Moon sinks off Green Cape, New South Wales, with the loss of 71 persons.
- 1942 – During the Attack on Sydney Harbour, a Japanese midget submarine sinks the converted ferry HMAS Kuttabul, killing 21.