Alexander Posey (c. 1794-?) was an American militia officer who served as a brigadier general under General Henry Atkinson during the Black Hawk War, specifically in the later stages of the second campaign as one of the commanders present at the Battle of Bad Axe.
Born in Orange County, Virginia to Revolutionary War General Thomas Posey and Mary Alexander, Alexander Posey was a physician in Gallatin County, Illinois when he was elected brigadier general by the volunteers gathered at Dixon's Ferry on June 13, 1832, possibly due to being the brother-in-law of U.S. Indian Agent Joseph Street. Assigned to command one of three brigades under General Henry Atkinson two days later, Posey was sent to Fort Hamilton accompanied by two companies of regulars under Hugh Brady on June 20.
On June 25, a detachment of soldiers from his command under Major John Dement were involved in a large skirmish with a Sauk war party under Neapope and Weesheet while encamped at Burr Oak Grove. Posey attempted to relieve Dement setting out from nearby Buffalo Grove, however the Sauk had retreated only two hours before his arrival. Five soldiers and twenty horses had been killed while nine Sauk were observed on the field. He briefly searched north for the raiding party then returned to Kellogg's Grove to await wait for the baggage-wagons before continuing on to Fort Hamilton where he made camp along the Pecatonica River on June 28.