Ryanair is an Irish ultra low-cost carrier group headquartered in Swords, Dublin, Ireland. The parent company Ryanair Holdings plc includes subsidiaries Ryanair DACTooltip Designated activity company, Malta Air, Buzz, Lauda Europe and Ryanair UK. Ryanair DAC, the oldest airline of the group, was founded in 1984. Ryanair Holdings was established in 1996 as a holding company for Ryanair with the two companies having the same board of directors and executive officers. In 2019 the transition began from the airline Ryanair and its subsidiaries into separate sister airlines under the holding company. Later in 2019, Malta Air joined Ryanair Holdings.

Ryanair has been characterised by its rapid expansion, a result of the deregulation of the aviation industry in Europe in 1997 and the success of its low-cost business model. The group operates more than 500 planes. Its route network serves over 40 countries in Europe, North Africa (Morocco and the Middle East (Israel, Jordan and Turkey). The primary operational bases are at Dublin, London Stansted and Milan Bergamo airports. Ryanair is Ireland's biggest airline and in 2016 became the world's largest airline by scheduled international passengers. Almost all the group's fleet are Boeing 737s.

The company has at times been criticised for its refusal to issue invoices for the VAT-exempt services it provides (airfares), poor working conditions, heavy use of extra charges, poor customer service, and tendency to intentionally generate controversy in order to gain publicity.