The Antonov An-225 Mriya (Ukrainian: Антонов Ан-225 Мрія, lit. 'dream' or 'inspiration'; NATO reporting name: Cossack) was a strategic airlift cargo aircraft designed and produced by the Antonov Design Bureau in the Soviet Union.

It was originally developed during the 1980s as an enlarged derivative of the Antonov An-124 airlifter for transporting Buran spacecraft. On 21 December 1988, the An-225 performed its maiden flight; only one aircraft was ever completed, although a second airframe with a slightly different configuration was partially built. After a brief period of use in the Soviet space programme, the aircraft was mothballed during the early 1990s. Towards the turn of the century, it was decided to refurbish the An-225 and reintroduce it for commercial operations, carrying oversized payloads for the operator Antonov Airlines. Multiple announcements were made regarding the potential completion of the second airframe, though its construction largely remained on hold due to a lack of funding. By 2009, it had reportedly been brought up to 60–70% completion.

With a maximum takeoff weight of 640 tonnes (705 short tons), the An-225 held several records, including heaviest aircraft ever built and largest wingspan of any operational aircraft. It was commonly used to transport objects once thought impossible to move by air, such as 130-ton generators, wind turbine blades, and diesel locomotives. Additionally, both Chinese and Russian officials had announced separate plans to adapt the An-225 for use in their respective space programmes. The Mriya routinely attracted a high degree of public interest, attaining a global following due to its size and its uniqueness.

The only completed An-225 was destroyed in the Battle of Antonov Airport in 2022 during the Russian invasion of Ukraine. Ukrainian president Volodymyr Zelenskyy announced plans to complete the second An-225 to replace the destroyed aircraft.