STS-119 was a Space Shuttle mission to the International Space Station (ISS) which was flown by Space Shuttle Discovery during March 2009. It delivered and assembled the fourth starboard Integrated Truss Segment (S6), and the fourth set of solar arrays and batteries to the station. The launch took place on March 15, 2009, at 19:43 EDT. Discovery successfully landed on March 28, 2009, at 15:13 pm EDT.

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.