Tianwen-1 (from Chinese: 天问一号, "celestial questions" in English) is a Martian space probe by the Chinese Space Agency (CNSA) developed and built by CASC, China's leading space industry. The probe consists of an orbiter, a lander, and a rover that will explore the planet's surface. After the failure in 2011 of the joint Sino-Russian Phobos-Grunt mission that carried the small Chinese satellite Yinghuo 1, it was finally decided to conduct the next Chinese mission independently. The successes of the Chang'e lunar exploration programme, in particular the landing system for Chang'e 3 and 4, provide sufficient technology for an ambitious mission. The project is approved in 2016, making it China's first interplanetary probe.

The spacecraft with a total weight of nearly 5 tons is one of the heaviest probes ever launched to Mars and carries a total of 13 scientific instruments. The orbiter, which has a lifespan of two years and is responsible for orbital manoeuvres, is equipped with two medium (MoRIC) and high-resolution (HiRIC) cameras, a ground-penetrating radar, an infrared spectrometer, a magnetometer, and two particle detectors. The 240 kg rover has a life span of 3 months and carries a stereoscopic navigation camera (NaTeCam), a multispectral camera, a ground-penetrating radar, a magnetometer, an imaging spectrometer (MarsCoDe), and a weather station. The scientific objectives of the mission focus on the geology of Mars, the present and past presence of water on and beneath its surface, and the interaction of its atmosphere with solar particles.

After two months of studying the landing site, the re-entry capsule will detach from the orbiter in April 2021 to perform an atmospheric re-entry, then release the lander to deposit the rover on the planet's surface. The orbiter will serve as a communications relay during the rover's primary mission and then move to a more suitable orbit for observations while maintaining its relay role.