The Essex coastal resort took the top spot in Rightmove's happy at home index in 2016 and has climbed back into first place 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.
Rightmove said Leigh-on-Sea scored highly for community spirit, the opportunity to develop skills, and restaurants and shops. Living in Leigh-on-Sea comes at an above-average price.
The average price of a home in the town is £386,613 - a 2% increase on this time last year and £82,552 higher than the national average of £304,061.
Last year's happiest place to live, Leamington Spa, came fifth in this year's survey.
Nowhere in Scotland made the top 10, with Edinburgh scoring best north of the border, but only 41st in the overall rankings.
The research found that Dumfries in Scotland scored particularly well for community spirit, while Caerphilly in Wales scored highly for friendly neighbours.
Leafy Richmond-upon-Thames was named the happiest place in London for the fourth year in a row, and was 29th overall.
The 10 happiest places to live according to Rightmove's survey: