Saint Dwynwen is the Welsh patron saint of lovers. She is said to have lived during the fifth century AD and was one of twenty-four daughters attributed to Saint Brychan.

In the tale told of her, Dwynwen falls in love with a young man named Maelon, but rejects his advances. Stories differ substantially on the events that followed but the outcome remains the same. Either she is raped by Maelon and prays for assistance, or she is unable to marry him due to her father's refusal and prays to forget her love for him. An angel provides her with a potion. Maelon drinks it and turns into ice. Dwynwen then prays for three requests (either given as a result of drinking the potion, or prayed for when she sees what happens to Maelon). These three requests are that Maelon be released; that, through her, God look after all true lovers; and that she remain unmarried. She then retreats to the solitude of Llanddwyn Island off the west coast of Anglesey to become a hermit until she died circa 460 AD. This site is still visited today.

Saint Dwynwen's day, Dydd Santes Dwynwen, is celebrated on January 25. Seen as something of a "Welsh Valentine's Day", from the 1960s it has increased in popularity as a day when cards are sent and events such as concerts or parties are held.