Place Eugène Flagey (in French: Place Eugène Flagey, in Dutch: Flageyplein, usually shortened to Flagey by locals), is a square in the Brussels municipality of Ixelles, Belgium. It was named in honour of Eugène Flagey, mayor of Ixelles from 1935 to 1953. With ten streets converging at Flagey Square, it is one of the best connected crossroads in the city, directly adjacent to the neighbouring Ixelles Ponds (the street separating them now will disappear). A large flood control reservoir (necessary due to the low-lying terrain and high groundwater level) and a parking lot have been built under the square.

The area comprising the square was covered by the Ixelles Ponds until 1860 when one of the original ponds was drained as part of new urban design.

Beginning in 2002 the square was extensively renovated. Prior to the renovation the square had been primarily used as an open air parking lot. The project was infamously delayed many times and all activity had to grind to a halt for sometimes months on end. The plans were remade in 2004 partially on the demand of the local residents' association. Among their demands were the complete ellimination of above ground parking in the square. The original plan was not deemed ambitious enough and a new competition was launched for international bids from different architects. Latz&Partner and D + A International eventually won the contract.

Official celebrations for the reopening of Flagey Square took place in July 2008. Events held included fireworks, concerts, guided visits and film screenings. However, at the time of the official opening, and still as of 2010, the subterranean parking which was built below the square was not opened. The risk of flooding as well as other structural problems forced authorities to keep the facility closed.