U Fleků is a pub and microbrewery in Prague, Czech Republic. It occupies buildings around a central courtyard at Křemencova 11 in New Town, (Praha 1), not far from the National Theatre. The front facade of the building has an old, highly decorated clock above its door.

Originally a family business, the pub was founded in 1499, and therefore celebrated its fifth centenary in 1999. It has been referred to as the oldest brewery in Prague. In 1762 the brewery was bought by Jakub Flekovský, which gave its current name : U Fleků means in Czech "At the Fleks'". It is a popular destination with Prague tourists. After World War II the company was nationalized, and control was transferred to a board of management appointed by the state. Following the Velvet Revolution, the company was privatized.

Customers can sit in the open air "beer garden" (on the model of the German Biergarten) or inside in the pub. There are eight halls (rooms) to choose from, with the most famous one, with its original designs, called “Akademie” (Academy). Most of the halls are open for large groups only (with total seating for 1200 people). Customers sit at, and often share, long wooden tables and benches. Often strolling accordion and/or tuba players provide entertainment, and some customers like to sing along. On some nights, there is also a live cabaret show (fee, reservations needed). It features international dance routines (including Czech polka) and comedy.