Muslim population stood at 3.9 million or 6.5 percent of the total UK population in 2021, up from 4.9 percent in 2011.
The United Kingdom has seen rapid growth in the Muslim population, according to a 10-yearly census carried out in 2021.
The Muslim population, which stood at 3.9 million or 6.5 percent of the population, up from 4.9 percent before, Office for National Statistics (ONS) said on Tuesday.
The next most common responses were Hindu (1 million) and Sikh (524,000), while Buddhists overtook Jewish people (273,000 to 271,000).
For the first time, fewer than half of people in England and Wales described themselves as Christian.
The census showed "no religion" was the second most common response after Christian.
The proportion of people who said they were Christian was 46.2 percent, down from 59.3 percent in the last census in 2011.
In contrast, the number who said they had no religion showed the highest growth overall, increasing to 37.2 percent of the population last year from a quarter in 2011.
The religion question was added to the UK census in 2001. It remains voluntary to answer, but 94 percent of respondents did, according to the ONS.
Separately, when people were asked about their ethnic group, 81.7 percent of residents in England and Wales identified as White, down from 86 percent a decade earlier, according to the census.
And 74.4 percent of the total population identified as White as well as English, Welsh, Scottish, Northern Irish or British.
The next most common ethnic group was Asian, Asian British or Asian Welsh accounting for 9.3 percent of the overall population - 5.5 million people, up from 4.2 million.
The number of people identifying as Black, Black British, Black Welsh, Caribbean or African was 2.5 percent of the population, up from 1.8 percent, taking the figure from 990,000 to 1.5 million.
One in 10 households across England and Wales are now made up of people from two or more different ethnic groups - an increase from 8.7 percent.