There are 2,500 taverns in Antwerp—one for every 200 inhabitants—and the city is the club-going capital of Belgium, which means that the centers of nightlife are abuzz until the wee hours of the morning. The narrow winding streets of The Grote Markt, around the cathedral in particular, are packed with cafés, bars, restaurants, and a few clubs; it's an area that's very popular with visitors and locals looking for a traditional ale or a nice meal. For the hipper, more artsy crowd, Mechelseplein is an area just coming to life and finding its feet, with plenty of the hip cafés, bars, and theaters. Alternatively, head south to Leuvenstraat, especially around the Museum van Hedendaagse Kunst (MuHKA), which teems with bars and clubs. You might even be able to catch a cabaret performance.
Along the waterfront at Vlaamse Kaai and Waalse Kaai, there's a large parking square where you'll find some of Antwerp's biggest clubs as well as a group of smaller pubs. Be advised, though, that they share the area with Antwerp's red-light district.