The Saitama Seibu Lions are a professional baseball team based in Tokorozawa, Saitama. It was established in 1950 and was a founding member of Japan's Pacific League. Its ballpark is the Seibu Prince Dome, and its team colors are navy-blue, white, and red.

Several Seibu Lions team members also played in Major League Baseball, including Daisuke Matsuzaka (Boston Red Sox, New York Mets and Cleveland Indians) and Kazuo Matsui (New York Mets).