The town originally took top spot in the 2016 index, and has climbed back into first place again this year.
The findings follow a survey of more than 21,000 people by Rightmove, which asked people how happy they are with where they live across 219 areas in Britain, based on factors such as community spirit, feeling safe, earning enough money to live comfortably, proximity to green spaces and amenities, friendliness and artistic and cultural activities.
Leigh-on-Sea scored highly for community spirit, the opportunity to develop skills, and restaurants and shops.
Valerie Morgan of Leigh-on-Sea Town Council said: "We’re all quite friendly here. People like to pass the time of day with one another, rather than ignore each other. There is also quite a large dog walking community down here so there’s lots of social interaction and people stopping and chatting to each other.”
Rob Cooke, director of Hunt Roche estate agents in Leigh-on-Sea, said: “There is just a lot going on, there are some pretty trendy parts of Leigh-on-Sea.”
The 10 happiest places to live according to Rightmove’s survey:
1. Leigh-on-Sea, East of England
2. Farnham, South East
3. Monmouth, Wales
4. Christchurch, South West
5. Leamington Spa, West Midlands
6. Newbury, South East
7. Macclesfield, North West
8. Hitchin, East of England
9. Tunbridge Wells, South East
10. Kendal, North West