At launch, Call of Duty: Modern Warfare 3 included 16 total multiplayer maps.
The 2011 game launched with a broad selection of traditional six-versus-six maps, including Dome, Hardhat, Resistance, Seatown, Village, and Underground. These maps supported the core multiplayer modes and were designed around varied combat spaces, from compact industrial areas to larger urban and desert environments.
The launch total refers to the maps available in the base game on release, not every map eventually added through downloadable content. Modern Warfare 3 later received additional multiplayer content through the Call of Duty: Elite program and paid map packs, so totals can appear higher when post-launch releases are included.
Another source of confusion is the similarly titled 2023 game, Call of Duty: Modern Warfare III. That title launched with 16 remastered maps from 2009’s Modern Warfare 2, but it is a separate release. In the original 2011 Modern Warfare 3, the canonical launch count was also 16, making the stored answer correct for the question as written.