The population of England and Wales increased by 7% between the last two census surveys, the largest growth seen since records began, the Office for National Statistics said.
There were 56.1 million people living in England and Wales on the day of Census 2011, an increase of 3.7 million since 2001, when there were 52.4 million people.
The survey painted a picture of an ageing population with one in six people in England and Wales aged 65 and over.
The number of people aged 90 and over increased to 430,000, compared with only 13,000 when the Census was carried out 100 years earlier in 1911.
The median age of the population increased from 35 in 2001 to 39 in 2011 and the Census showed there are just under a million more women than men in England and Wales.
Children aged five or under also increased by more than 400,000 to 3.5 million.
Every region in England and Wales had a larger population in 2011 than 10 years earlier with the largest increase in London, which grew by 12%, taking its population to more than eight million.
The total population figure was about half a million larger than estimates had shown a year earlier.
Figures for Scotland will be released later this year.
2011 Census in numbers:
- England and Wales population: 56.1 million.
- Northern Ireland population: 1.8 million.
- Number of women: 28.5 million.
- Number of men: 27.6 million.
- Number of households: 23.4 million.
- Number of children under five: 3.5 million.