Amazon is accused of infringing on five IBM patents, including technologies that govern how the site handles customer recommendations, advertising and data storage.
IBM said hundreds of other companies have licensed the same patents, and that it tried to negotiate licensing fees with Amazon "over a dozen times since 2002" but "Amazon.com has refused every time."
A call to Amazon for comment was not immediately returned Monday morning.
IBM said its two lawsuits were filed in U.S. District Court in the Eastern District of Texas, one in the Tyler Division and the other in the Lufkin Division. Texas has emerged as a frequent site for patent cases in recent years because of a perception that certain districts there are more responsive to such claims.
IBM shares were up 20 cents at $90.68 on the New York Stock Exchange, while Amazon shares were down 27 cents at $32.30 on the Nasdaq Stock Market.
Both companies have relied heavily on patents. IBM is the world's leading patent holder, while Amazon famously patented its "one-click" checkout method in 1999. The U.S. Patent and Trademark Officeis re-examining that patent, which has long been criticized as overly broad.