The centre/wing made 260 appearances for Tigers following his debut in October 1996, with perhaps his most memorable achievement coming as a double try-scorer in the Heineken Cup Final against Stade Francais in 2001.
The 29-year-old has just completed his testimonial season at Welford Road after 10 years of loyalty in a glittering club career.
"Leicester is a fantastic rugby club and I am very fortunate to be able to say I was involved in one of the most successful periods in their history, particularly this season in winning the double," said Lloyd, who made 16 appearances in all competitions in 2006/07.
"I owe a tremendous debt of gratitude to many different people for what I have been able to achieve and it is something I will never forget. To have spent 10 years at one club has been a privilege and honour and their support throughout has been wonderful.
"But now I have the opportunity to experience a new culture at a club who are trying to create their own period of history in the English game. It is a brilliant challenge and the way Dean Ryan has recruited for next season and beyond, it is clear to me Gloucester are going in a hugely exciting direction and that is something I really want to be a part of."
Ryan, Gloucester's head coach, said that Lloyd would add experience and versatility to the side: "Leon is a tremendously gifted and adaptable player and someone we are thrilled to have in our squad. He will offer a significant attacking threat, is powerful, strong and has an excellent try-scoring record at the highest levels. Having played in 50 Heineken Cup matches, his experience alongside our younger backs will be invaluable."