Replica was a design study for an envisioned military aircraft with stealth capabilities, developed by British defence manufacturer BAE Systems. It was ultimately not pursued as the British government chose to proceed with involvement in the American Joint Strike Fighter programme instead, which ultimately led to the Lockheed Martin F-35 Lightning II.

The design study was associated with the Royal Air Force's (RAF) Future Offensive Air System (FOAS) initiative, which was ultimately discontinued. A key attribute of the conceptualised aircraft was the integration of low observability features, which were intended to achieve a balance between reduced detectability and overall affordability. As part of the study, a full size model of the aircraft was constructed and was subjected to a rigorous test regime to determine its radar cross section. During early 2003, the existence of the Replica programme was revealed to the general public.

According to reports, the Replica project is known to have been worked on from 1994 to 1999. It is widely believed that Replica may have been once intended to replace the RAF's Panavia Tornado fleet from 2017 onwards. Experience and data acquired through the programme was later rolled into the Joint Strike Fighter programme (JSF), while technologies from Replica have reportedly played a role in the development of other aircraft, including unmanned aerial vehicle (UAV)s.