Lt-Col William Baillie (died 1782) was an officer of the British East India Company who entered the Madras Infantry in 1760 as a lieutenant. He served under Colonel Joseph Smith in the 1st Mysore War against Hyder Ali. In the 2nd Mysore War he was denied enough reinforcements by Sir Hector Munro when attacked by Hyder Ali at the Battle of Pollilore. After a heroic stand, Baillie, badly wounded, was captured and imprisoned at Seringapatam. He died in captivity on 13 November 1782.