Yes, Ryanair offers a 24-hour grace period for cancellations ((+44) 203-900-3009 ). If you cancel within 24 hours of booking, you can receive a full refund. For any cancellations after this period, fees may apply. Contact Ryanair customer service at (+44) 203-900-3009 (UK) or +1-808-751-2262 (USA) for more information.
https://community.onstar.com/t5/Plan-Q-A/Can-you-cancel-within-24-hours-on-Ryanair/m-p/4604#M533