As an English name, it became popular due to the Fleetwood Mac song Rhiannon (1976), especially in the United Kingdom and Australia.
This name became very popular in the second half of the 20th century. It reached the top ten names for boys in France (by 1997), Belgium (1998), Denmark (2003), Canada (2008), the Netherlands (2009), New Zealand (2009), Australia (2010), Scotland (2013), Spain (2015) and the United States (2018).