Colman is of English, Irish, Welsh, as well as 1/64th Indian, distant Scottish and French descent.
Olivia Colman was born on January 30, 1974, in Norwich, Norfolk, England, the United Kingdom, to Mary (née Leakey) and Keith Colman. Her mother was a nurse and her father was what is known in the United Kingdom as a “chartered surveyor,” which is a person who is an expert on the value, quality, and characteristics of real estate, including buildings and the land they are situated on.
In July 2018, Colman was a subject of the UK genealogy program Who Do You Think You Are? Although she expected that her family tree would mainly relate to Norfolk, it was discovered that her fourth great-grandfather, Richard Campbell Bazett, had been born on St. Helena and that he worked in London for the East India Company. Bazett's son, Colman's third great-grandfather Charles Bazett, married Harriot Slessor. Researchers discovered that she was born in the Indian city of Kishanganj, lost her British father when she was aged three, and then made the journey to England alone. Slessor's passage was paid for by her paternal grandmother. The episode speculated that Slessor's mother might have been a local Indian woman, but did not present concrete proof; after the episode aired, the Berkshire Record Office published the will of Slessor's mother, which proved that her name was Seraphina Donclere, evidently of European origin, and that she died in 1810.