The 25-year-old road racing cyclist from Holloway in London finished 39 seconds ahead of Australian Jai Hindley in the 15.7km time trial in Milan on Sunday.
British-Kenyan Chris Froome is the only other UK male rider to win the Giro, doing so in 2018.
Geoghegan Hart follows Sir Bradley Wiggins, Chris Froome, Geraint Thomas and Simon Yates in winning a European Grand Tour.
While he was born in England, Geoghegan Hart has Scots-Irish ancestry and has expressed his desire to race for Scotland on numerous occasions.
Tao’s father Tom Geoghan was born in Scotland and his grandmother still lives in Edinburgh.
A cycling fan from a young age, Geoghegan Hart attended the 2007 Tour de France and was present at the launch of Team Sky in 2009, the team he would later join as a competitor.
As a teenager, Geoghegan Hart, whose partner Hannah Barnes is also a professional cyclist, competed with East London’s Cycling Club Hackney and quickly rose to prominence after a string of victories and podium places.
He is also a keen swimmer and was part of a cross-Channel swimming realy with Clissold Swimming Club when he was aged 13.
After a stint with Bissell Development Team and achieving the best young rider classification at the USA Pro Cycling Challenge in 2015, Geoghegan Hart began his Team Sky career at professional level in 2016 and was named in the start list for the 2018 Vuelta a Espana and the startlist for the 2019 Giro d’Italia.
Following a sponsorship switch, Geoghegan Hart races under the Ineos Grenadiers banner, formerly Team Sky from 2010 to 2019 and Team Ineos from 2019 up until this year.
Geoghegan Hart was selected to represent Scotland for the last two Commonwealth Games, but was unable to find time in his race schedule to appear at either competition.
The cyclist is now targeting the Birmingham Commonwealth Games in 2022 and said last year it would “definitely” be in Scotland’s colours.