Nicholas David Barratt is an English genealogist, broadcaster and historian and is currently the Executive Director of Student Journey at Royal Holloway University of London. He was the original genealogical consultant and on-screen expert for series 1 to 4 of the BBC show Who Do You Think You Are? and worked on the format in the Republic of Ireland and Australia. Barratt has made other TV appearances, written books and been the President of the Family History Federation, Trustee of the Society of Genealogists and board member for the Community Archives and Heritage Group. He is a Fellow of the Royal Historical Society.

Who Do You Think You Are? is a British genealogy documentary series that has aired on the BBC since 2004, in which celebrity participants trace their family history. It is made by the production company Wall to Wall. The programme has regularly attracted an audience of more than 6 million viewers. More than ten international adaptations of the programme have been produced.