The population of England and Wales has increased by more than 7% during the last 10 years - the biggest increase since records began.
There were 56.1 million people living in England and Wales on the day of last year's Census - an increase of 3.7 million since 2001, the Office for National Statistics (ONS) said.
This marks the largest growth in population in any 10-year period since the first Census in 1801, and a rise of approximately 50% since 1911.
The number of households in England and Wales increased by 8% to 23.4 million - although the average size remained unchanged at 2.4 people.
The once-a-decade survey from 2011 illustrated an aging population, with one in six people in England and Wales aged 65 or over.
There were also 430,000 people aged 90 or over - compared with just 13,000 when the Census was carried out 100 years earlier.
The number of women to reach this age was more than three times higher than the number of men.
But the amount of children under the age of five was also up, with 400,000 more last year than in 2001.
London experienced the largest population boost - surging by 12% to a total of more than eight million - although the figures showed an increase in every region in England and Wales over the decade.
In total, England's population hit 53 million, Wales' reached 3.06 million and Northern Ireland's increased to 1.8 million. Figures for Scotland will be released later in the year.
The ONS estimates that around 55% of the increase in population between 2001 and 2011 was the result of net migration.
National Statistician Jil Matheson described the 2011 Census as a "resounding success".
"Across England and Wales around 19 out of 20 people responded and we have excellent statistical methods for ensuring we have a complete estimate of the whole population," she said.
"These statistics will provide valuable information for planners, policy-makers and the public for years to come."