STS-133 was the 133rd mission in NASA's Space Shuttle program; during the mission, Space Shuttle Discovery docked with the International Space Station. It was Discovery's 39th and final mission. The mission launched on February 24, 2011, and landed on March 9, 2011. The crew consisted of six American astronauts, all of whom had been on prior spaceflights, headed by Commander Steven Lindsey. The crew joined the long-duration six person crew of Expedition 26, who were already aboard the space station. About a month before lift-off, one of the original crew members, Tim Kopra, was injured in a bicycle accident. He was replaced by Stephen Bowen.

The process of assembling the International Space Station (ISS) has been under way since the 1990s. Zarya, the first ISS module, was launched by a Proton rocket on 20 November 1998. The STS-88 Space Shuttle mission followed two weeks after Zarya was launched, bringing Unity, the first of three node modules, and connecting it to Zarya. This bare 2-module core of the ISS remained uncrewed for the next one and a half years, until in July 2000 the Russian module Zvezda was launched by a Proton rocket, allowing a maximum crew of three astronauts or cosmonauts to be on the ISS permanently.