火星勘测轨道飞行器（Mars Reconnaissance Orbiter，缩写MRO）是美国国家航空航天局的2005年火星探测计划之一。这项计划的主要目的是将一枚侦察卫星送往火星，以前所未有的分辨率对火星这颗红色行星进行详细考察，并且为往后的火星地表任务寻找适合的登陆地点，同时为这些任务提供高速的通信传递功能。这项计划预计将在火星轨道运行至少四年，并且成为火星的第三个正在使用中的人造卫星（前二个为火星快车号、2001火星奥德赛号）与第五个正在使用中的火星探测器（三个卫星加上两台火星探测漫游者）。

Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. The US$720 million spacecraft was built by Lockheed Martin under the supervision of the Jet Propulsion Laboratory (JPL). The mission is managed by the California Institute of Technology, at the JPL, in La Cañada Flintridge, California, for the NASA Science Mission Directorate, Washington, D.C. It was launched August 12, 2005, and attained Martian orbit on March 10, 2006. In November 2006, after five months of aerobraking, it entered its final science orbit and began its primary science phase. As MRO entered orbit, it joined five other active spacecraft that were either in orbit or on the planet's surface: Mars Global Surveyor, Mars Express, 2001 Mars Odyssey, and the two Mars Exploration Rovers (Spirit and Opportunity); at the time, this set a record for the most operational spacecraft in the immediate vicinity of Mars. Mars Global Surveyor and the Spirit rover have since ceased to function; the remainder remain operational as of March 2016.