The Tropical Rainfall Measuring Mission (TRMM) was a joint space mission between NASA and JAXA designed to monitor and study tropical rainfall. The term refers to both the mission itself and the satellite that the mission used to collect data. TRMM was part of NASA's Mission to Planet Earth, a long-term, coordinated research effort to study the Earth as a global system. The satellite was launched on 27 November 1997 from the Tanegashima Space Center in Tanegashima, Japan. TRMM operated for 17 years, including several mission extensions, before being decommissioned on 15 April 2015. TRMM re-entered Earth's atmosphere on 16 June 2015.

Tropical precipitation is a difficult parameter to measure, due to large spatial and temporal variations. However, understanding tropical precipitation is important for weather and climate prediction, as this precipitation contains three-fourths of the energy that drives atmospheric wind circulation. Prior to TRMM, the distribution of rainfall worldwide was known to only a 50% of certainty.

The concept for TRMM was first proposed in 1984. The science objectives, as first proposed, were:

Japan joined the initial study for the TRMM mission in 1986. Development of the satellite became a joint project between the space agencies of the United States and Japan, with Japan providing the Precipitation Radar (PR) and H-II launch vehicle, and the United States providing the satellite bus and remaining instruments. The project received formal support from the United States Congress in 1991, followed by spacecraft construction from 1993 through 1997. TRMM launched from Tanegashima Space Center on 27 November 1997.

The Tropical Rainfall Measuring Mission (TRMM), one of the spacecraft in the NASA Earth Probe series of research satellites, is a highly focused, limited-objective program aimed at measuring monthly and seasonal rainfall over the global tropics and subtropics. TRMM is a joint project between the United States and Japan to measure rainfall between 35.0° North and 35.0° South at 350 km altitude.

To extend TRMM's mission life beyond its primary mission, NASA boosted the spacecraft's orbit altitude to 402.5 km in 2001.

In 2005, NASA director Michael Griffin decided to extend the mission again by using the propellant originally intended for a controlled descent. This came after a 2002 NASA risk review put the probability of a human injury or death caused by TRMM's uncontrolled re-entry at 1-in-5,000, about twice the casualty risk deemed acceptable for re-entering NASA satellites; and a subsequent recommendation from the National Research Council panel that the mission be extended despite the risk of an uncontrolled entry.

Battery issues began to limit the spacecraft in 2014 and the mission operations team had to make decisions about how to ration power. In March 2014, the VIRS instruments was turned off to extend the battery life.