The Folland Gnat was an exceptionally small swept-wing subsonic jet trainer and light fighter aircraft designed by W. E. W. Petter that first flew in 1955. Its design was such that it could be built without specialised tools, hence by countries that were not necessarily in the first rank of industrialisation. However, to achieve such small size, its systems were quite closely-packed, making maintenance more difficult.

Serving mostly with India as the Gnat Mk.II, the Gnat is credited with shooting down seven Pakistani F-86s in the 1965 war between the two countries.

In Britain it served as the Folland Fo.144 Gnat Trainer (later renamed the Gnat T.Mk1), most notably as the demonstration aircraft of the RAF's Red Arrows aerobatic team. A few served with Finland.

Many of the Indian aircraft were built in Bangalore with over 175 made there along with about 40 purchased direct from Folland. Finland had stopped using Gnats by 1974, and the UK by 1979. Gnats served in India from 1958-1978, and several remain in use in private hands.

The Gnat's experimental precursor was the Folland Midge , which used a less-powerful engine. In India, the aircraft was called the Ajeet , or "Unconquerable". The successor of the Gnat was a modification for Indian conditions, called the Ajeet Mark 2.

When the RAF replaced and sold-off its Gnat T.Mk1 trainers many were bought by private collectors and subsequently appeared (along with some single-seat Gnats) in the Charlie Sheen movie Hot Shots.