The McFly drummer has been dating violinist Izzy Johnston ever since her band Escala supported his group on tour in 2005.
"I liked it, so I put a ring on it. #engaged," Judd wrote on Twitter today (May 17).
Judd and Johnston moved in together last summer, shortly before Judd was confirmed as a contestant on the 2011 edition of Strictly Come Dancing.
After his Strictly win, Judd said that he planned to propose to Johnston but he also wanted it to be a "complete surprise" and "as romantic and spontaneous as possible".
The musician previously admitted that he wanted "marriage, kids, the whole deal" with Johnston, adding that she was "the only girl in the world" for him.
Judd's bandmate Tom Fletcher married his long-term girlfriend Giovanna Falcone earlier this month.
McFly's Danny Jones and Dougie Poynter joined Judd as Fletcher's best men at the ceremony at One Marylebone.
Meanwhile, Jones has claimed that his own girlfriend Georgia Horsley has rejected five wedding proposals from him during their two-year relationship.