The mission code for the final Space Shuttle flight in July 2011 was STS-135.
Atlantis launched from Kennedy Space Center's Launch Complex 39A on July 8, 2011, carrying commander Christopher Ferguson, pilot Douglas Hurley, and mission specialists Sandra Magnus and Rex Walheim. The mission delivered the Raffaello multipurpose logistics module to the International Space Station.
STS-135 was the 135th numbered Space Transportation System mission and Atlantis's 33rd flight. It lasted 12 days, 18 hours, and 28 minutes, ending with a landing at Kennedy Space Center on July 21. That touchdown closed the Space Shuttle era after 30 years of flights.
A common mix-up is confusing STS-135 with STS-134, which was Endeavour's final mission and flew in May 2011. STS-133 was Discovery's final flight, while STS-132 was Atlantis's penultimate mission. The number therefore identifies a specific mission, not the shuttle orbiter itself.