The Walther P99 (German: [ˈvaltɐ]) is a semi-automatic pistol developed by the German company Carl Walther GmbH Sportwaffen of Ulm for law enforcement, security forces and the civilian shooting market.

Design work on this new generation sidearm began in 1994, and the handgun was presented in 1997 with series production commencing that same year as a replacement for the Walther P5 and the P88.

Walther announced the discontinuation of the P99 in early 2023.

The Walther P99 was modified several times throughout its production history, as were the magazines.

When the P99 was introduced the magazine capacities were 16 rounds for 9×19mm Parabellum and 12 rounds for .40 S&W.

Magazines had witness holes on both sides. Later the magazine capacities were reduced to 15 rounds for 9×19mm Parabellum and 11 rounds for .40 S&W while witness holes were introduced at the rear of the magazine to view the loading condition.

Walther presented a redesigned second generation P99 in 2004, incorporating a modified trigger guard that eliminated the "ski hump", which is clearly visible in the accompanying first generation images, to address user comfort concerns regarding the previous style.

The first generation P99 pistols had a slide release at the left side of the frame while second generation guns may have optional ambidextrous slide stop release levers.