| Alexander Hay | |
| Birth Date: | 8 April 1806 |
| Birth Place: | Scotch Hill, Pittsburgh, Pennsylvania |
| Office: | 12th Mayor of Pittsburgh |
| Term Start: | 1842 |
| Term End: | 1845 |
| Predecessor: | James Thomson |
| Successor: | William J. Howard |
| Allegiance: |  United States |
| Rank: | Captain |
| Battles: | Mexican–American War American Civil War |
Alexander Hay (April 8, 1806 - November 5, 1882) was Mayor of Pittsburgh, USA, from 1842 to 1845.
Hay was born in the neighborhood known as Scotch Hill. By age eleven, he worked in a glass house and learned the trade of cabinetry.
The Roman Catholic Diocese of Pittsburgh was created during Mayor Hay's term. Also, navigation on the Monongahela River was opened as far south as Brownsville during his administration.
Hay's life of public service continued after his term as mayor. He commanded the Jackson Blues during the Mexican War. During the Civil War, he was captain of Company E. Pennsylvania Regiment. He was at the Battle of Yorktown.
He and his son were the proprietors of a fine furniture business. Hay died in 1882 and is buried in the Allegheny Cemetery.