The low cost airline is understood to have selected Isango and integrated its search and booking facilities into its website over the course of the past few months, but so far avoided publicising the partnership.
The system is a pure white label of the Isango consumer website and includes search tools by destination and trip type. Users can also complete the booking on the Ryanair site.
The deal is the latest – and probably the biggest – trade deal for the Isango brand following its launch in late-2006.
Other recent white labels signed by Isango include Hertz, WAYN.com, Zoom Airlines, Yahoo Travel and Kelkoo.
Isango also won the right to provide tours and trips functionality on a website promoting the recent Seven Wonders of the World competition.
The company declined to comment on the Ryanair partnership.