| William James Alexander Weir | |
| Birth Date: | 4 April 1891 |
| Death Date: | 28 September 1917 |
| Birth Place: | Leichhardt, New South Wales |
| Allegiance: | Australia |
| Branch: | Australian Imperial Force (1914–17) Australian Flying Corps (1917–18) |
| Serviceyears: | 1914–1918 |
| Rank: | Lieutenant |
| Unit: | No. 1 Squadron AFC |
| Awards: | Distinguished Flying Cross |
William James Alexander Weir, (born 4 April 1891) was an Australian flying ace of the First World War credited with six aerial victories. He received the Distinguished Flying Cross for "conspicuous gallantry in air combats and attacking ground objectives".[1] [2]