The Diamond DV20/DA20 Katana is an Austrian-designed two-seat general aviation light aircraft. Developed and manufactured by Diamond Aircraft, it was originally produced in Austria as the DV20.

The DV20 shares many features from the earlier Diamond HK36 Super Dimona. It was introduced to service during 1993. During the 1990s, production of the type was commenced at a new facility in Canada in order to meet demand for the type within the North American market. The Canadian-produced aircraft are designated as the DA20. It has been a relative success on the market, having sold in excess of 1,000 aircraft by 2008 and multiple improved variants of the DA20 have been developed. Additionally, it has been further developed into the four-seat Diamond DA40 Diamond Star.

In 1981, a new company, Hoffmann Flugzeugbau, was formed in Austria with the aim of becoming a major aircraft manufacturer for general aviation purposes. During the late 1980s, management at the firm continued to rapidly expand its range of products; it also underwent several changes in name and ownership, eventually becoming Diamond Aircraft. It was decided to develop a new two-seat aircraft, later designated as the DV20 Katana, using the earlier and successful Diamond HK36 Dimona as a basis.

The DV20, while owing much of its design and sharing many features of the Dimona, had several major differences as well. In particular, it had a reduced wingspan, was equipped with flaps, and made use of a tricycle landing gear arrangement. The Katana has also been developed with a philosophy of offering aircraft that weren't equivalent in terms of performance to any major existing product from competing manufacturers, consciously avoiding instances of direct head-to-head competition. In 1991, the Katana conducted its maiden flight; during May 1993, the type received certification. In 1993, the Katana was first displayed to the general public at the Paris Air Show.

Originally placed into production in Austria, during the early 1990s, a purpose-built factory was established by Diamond in London, Ontario, Canada to produce the DV20, which was subsequently designated as the DA20. The DA20 featured around 40 individual improvements, having been effectively revamped to take on the competitive general aircraft market in the region. According to aerospace publication Flight International, the decision to transfer production to Canada was to meet demand for such an aircraft within the sizable North American market; in addition, the firm already considered itself secure in its dominance in the European general aircraft market. In 1994, the first Canadian-produced DA20, a Rotax 912-powered A1 aircraft, was completed; it was the first Diamond aircraft available for sale in North America. Between 1994 and 1999, in excess of C$100 million was invested in the Canadian plant.

During 1998, production of the Continental IO-240-B3B-powered C1 Evolution and Eclipse models commenced, which was also performed at the firm's Canadian facility. The C1 model featured several advances, including the adoption of a new engine, which was more powerful than the Rotax 912 and provided the plane with greater performance as a result; other improvements included increased comfort, the adoption of slotted-flaps, and an improved braking capability. During the late 1990s, Diamond also developed a new four-seat aircraft, designated as the DA40, which had been heavily derived from the DA20.

Both the DA20-A1 and C1 are certified under AWM 523-VLA in Canada, as well as being under FAR 23 in the USA. The DA20 is certified in the utility category; in particular, it is permissible to intentionally spin it with flaps in the full up position. In 2004, Diamond received Chinese certification for the DA20. Both models also hold Joint Aviation Authorities (JAA) certification.

Although the DA20 is available with instrumentation and avionics suitable for flight under instrument flight rules (IFR), its plastic airframe lacks lightning protection and thus does not qualify for IFR certification. This limitation is not viewed as being relevant to most potential customers; according to aircraft publication Flying, "even when there were a lot of two-place trainers, there wasn't a lot of instrument training done in them...not too many owners of two-seaters fly them IFR".