STS-129 (ISS assembly flight ULF3) was a NASA Space Shuttle mission to the International Space Station (ISS). Atlantis was launched on November 16, 2009 at 14:28 EST, and landed at 09:44 EST on November 27, 2009 on runway 33 at the Kennedy Space Center's Shuttle Landing Facility. It was also the last shuttle launch of the 2000s.

STS-129 focused on staging spare components outside the station. The 11-day flight included three spacewalks. The payload bay carried two large ExPRESS Logistics Carriers holding two spare gyroscopes, two nitrogen tank assemblies, two pump modules, an ammonia tank assembly, a spare latching end effector for the station's robotic arm, a spare trailing umbilical system for the Mobile Transporter, and a high-pressure gas tank. STS-129 was the first flight of an ExPRESS Logistics Carrier. The completion of this mission left six Space Shuttle flights remaining until the end of the Space Shuttle program, after STS-135 was approved in February 2011.

Short-term experiments included:
Shuttle Exhaust Ion Turbulence Experiments (SEITE) – The crew of Atlantis carried out the SEITE burn on Flight Day 11. SEITE uses instrumentation on The Communications/Navigation Outage Forecasting System (C/NOFS) satellite for in situ observations of density and electric field disturbances caused by the shuttle Orbital Maneuvering System (OMS) engine exhaust plume. The scope of the research is to enhance the surveillance of space, real-time characterization, detection and tracking and timely surveillance of high interest objects.
Shuttle Ionospheric Modification with Pulsed Localized Exhaust Experiments (SIMPLEX) – The crew carried out the SIMPLEX burn on Flight Day 11. The experiment investigates plasma turbulence driven by shuttle exhaust in the ionosphere using ground-based radars. The processes by which chemical releases can produce plasma turbulence are quantified with the SIMPLEX measurements. Plasma turbulence can affect military navigation and communications using radio systems. They can also be used to promote communications by opening radio channels at abnormally high frequencies.

New experiments delivered to the space station included:
Microbe experiment – An experiment developed by Texas Southern University (TSU) students in Houston that aims to study how microbes (Escherichia colii and Bacillus subtilis) grow under weightless conditions in space. Students at TSU, Centre for Bionanotechnology and Environmental Research (CBER) will share experimental data with K-12 students nationwide. additional information on the experiment named "URC Microbial 1"
Butterflies in Space Program – The shuttle carried a suitcase sized payload holding larvae of painted lady butterflies and monarch butterflies to the space station. Researchers at the University of Colorado in Boulder expect to compare the space caterpillars with butterfly larvae raised on Earth by students from 100 U.S. elementary and middle schools. Visit http://www.bioedonline.org to follow the ground-based experiment on Earth at Baylor College of Medicine in Houston, or to download the Butterflies in Space free teacher's guide for classroom use.
Advanced Plant Experiments on orbit (APEX-Cambium project) – This joint Canadian Space Agency/NASA project aims to help determine the role gravity plays in the formation of reaction wood in trees.APEX-Cambium will also carry out a second experiment to detect the effects of stressors in space on gene expression in higher plants.
Atlantis transported thousands of the microscopic Caenorhabditis elegans worms that have been sent from the University of Nottingham, UK to the ISS. The worms are expected to suffer similar muscle loss to humans and will be stored inside the Kibo laboratory. They will be used to study the effect of zero gravity on the human body's muscle development and physiology. Several potential treatments for muscle loss will be tested on the creatures and the research findings will pave the way for treatments to be safely tested on astronauts.