The aircraft took off just before 9am heading to Girona in Spain.
It then declared an emergency over France and was directed to make an unscheduled landing at Paris Beauvais Airport.
A passenger is believed to have been taken ill and medical teams met the flight to provide treatment.
It is scheduled to land in Girona at 11.45am local time.
Leeds Rhinos are due to play Super League side Catalan Dragons in nearby Perpignan on Saturday night, and travelling Rhinos fans are expected to be among the passengers.
A statement from Ryanair said:
"This flight from Leeds Bradford to Girona diverted to Paris Beauvais after a customer became ill on board. The crew called ahead to request medical assistance, the aircraft landed normally and the customer disembarked and was met by medics for further treatment. The aircraft will depart to Girona shortly and Ryanair apologised to customers for the short delay to their flight.”