The airline will introduce the service next month on its Dublin to London Gatwick and Malaga routes. It said that if it proves popular it will roll it out on other routes.
Customers will be able to book seats in the front two rows of the plane and in the emergency exit-row seats, which offer more leg room. For the €10 price each way customers will also receive priority boarding.
However, priority boarding only will remain an option at €4 each way.
The move will potentially earn the airline €240 per flight. It is the first time since adopting the low-cost model 25 years ago that Ryanair will offer reserved seating.
The service is likely to be popular with business travellers. Easyjet recently said it is trialling new incentives for business travellers on Scottish routes.
This latest move is seen as a U-turn for the airline as it is standard among low-cost operators that seat reservations could hamper the fast turnaround times.
Gert Zonneveld, an analyst at Panmure Gordon, said: “Reserving seats is a reasonably low-cost way of squeezing a bit more cash out. There will be demand for this and people who will take it up.”
This news follows a recent announcement from Ryanair that it has added a €2 levy to fares in order to cover costs of compensating passengers under European law.
The airline said it was adding the levy because it had suffered costs of more than €100 million over the past year, most of which arose from times when it could not fly for reasons beyond its control.
Ryanair spokesman Stephen McNamara said is “clearly unfair” that airlines are obliged to provide meals and accommodation for passengers because “governments close their airspace, or air traffic controllers walk off the job or incompetent airports fail to clear their runways of snow”.
“While we regret the imposition of this levy, the extraordinary costs which have been imposed on us by delays and cancellations under these discriminatory regulations must be recovered from passengers.”