The Aero L-39 Albatros is a high-performance jet trainer aircraft developed in Czechoslovakia to meet requirements for a "C-39" (C for cvičný – trainer) during the 1960s to replace the L-29 Delfín. It was the first of the second-generation jet trainers, and the first turbofan-powered trainer produced, and was later updated as the L-59 Super Albatros and as the L-139 (prototype L-39 with Garrett TFE731 engine).

A further development of the design, the L-159 ALCA, began production in 1997. To date, more than 2,800 L-39s have served with over 30 air forces around the world. The Albatros is the most widely used jet trainer in the world; in addition to performing basic and advanced pilot training, it has also flown combat missions in a light-attack role. Atypically, it has never received a NATO reporting name.

While newer versions are now replacing older L-39s in service, thousands remain in active service as trainers, and many are finding new homes with private warbird owners all over the world. This is particularly evident in the United States, where their $200,000–$300,000 price puts them in range of moderately wealthy pilots looking for a fast, agile personal jet. Their popularity led to a purely L-39 Jet class at the Reno Air Races, though it has since been expanded to include other, similar aircraft.

In September 2012 there were 255 L-39s registered with the US Federal Aviation Administration and four registered with Transport Canada.  Several display teams use the L-39 such as the Patriots Jet Team (6 L-39s), the Breitling Jet Team (7 L-39s) and the Black Diamond Jet Team (5 L-39s).

There are also several L-39 available for private jet rides in Australia, Czech Republic, France, Germany, Spain and the USA.  These L-39s are mostly in private hands, but some also belong to government agencies, such as those in Vyazma, Russia.