The 2004 release Harry Potter and the Prisoner of Azkaban was the third film in the series.
Erin's rep told Mail Online the couple have been dating 'for about two years'.
He made his acting debut at 10 years of age in BBC One's 1999 television film David Copperfield, followed by his cinematic debut in 2001's The Tailor of Panama.
At age 11, he was cast as Potter in the series' first film The Philosopher's Stone, and starred in the series for 10 years until the release of the eighth and final film, The Deathly Hallows – Part 2 in 2011.
Radcliffe stated that director David Yates and actress Imelda Staunton made Order of the Phoenix the "most fun" film in the series to work on.
In July 2009 Harry Potter and the Half-Blood Prince was released, the series' sixth instalment.