The Marcus Amphitheater is the highlight of the Henry Maier Festival Grounds, or more widely known as the Summerfest Milwaukee. The festival grounds are located on the Lake Michigan shoreline, and is home to a variety of events, most popular being Summerfest itself. The Marcus Amphitheater is located on the south end of the grounds.

The Marcus Amphitheater was built in 1987 to help cater to crowds of twenty-thousand concertgoers.  It is an outdoor amphitheater with both a covered seating area and lawn seating. The major donor that brought the project to reality was from the Marcus Corporation, hence the name of the theater. The venue seats 25,000 and has great views of the Milwaukee skyline and Lake Michigan.

During Summerfest, and throughout the rest of the festival season, the Marcus Amphitheater hosts very popular musical acts, including performances in the past from John Mayer, Steve Miller Band and Tom Petty and the Heartbreakers.