Luke Robertson, from Stonehaven in Aberdeenshire, reached the Pole at around 2.30am yesterday after 39 days skiing unassisted in “unforgiving” Antarctic conditions, cancer charity Marie Curie said.
He is also the first Scot to achieve the feat, which has raised £47,000 for the charity.
Mr Robertson, who lives in Edinburgh, dragged 130kg of equipment across miles of ice and snow, burned more than 400,000 calories and climbed twice the height of Ben Nevis, while braving temperatures of -50C and up to 100mph winds.
He set off from Hercules Inlet on the edge of Antarctica on 5 December, spending Christmas Day alone.
Speaking from the South Pole, he thanked supporters “around the world” for their messages.
“What an unbelievable and surreal feeling. I feel on top of the bottom of the world!” he said. “All those months of training and preparation have really paid off, but I couldn’t have done it without the support of so many people who have helped to make this expedition a success. In particular, my fiancée Hazel, my parents, family, friends and colleagues for their unwavering support.
“Thank you so much to everyone who has donated to Marie Curie; they are an incredible charity, very close to my heart, and I feel so proud to be representing them on this expedition.
“It’s amazing to repay the faith put in me by all my supporters. Now, I think it’s time for a big feed, a wee dram and a shower.”
Supporters, including explorer Sir Ranulph Fiennes, congratulated him. Sir Ran said: “I am delighted that Luke has reached the South Pole and becomes the youngest Brit ever to do so, unaided. It is an incredible achievement.”
Dr Jane Collins, chief executive of Marie Curie said: “We’d like to say a huge congratulations and thank you to Luke. His record-breaking solo adventure to the South Pole for Marie Curie shows that through sheer determination anything is possible. ”
The adventurer was inspired to embark on the challenge after overcoming a series of health problems, including surgery to remove a suspected brain tumour a year ago, which turned out to be a cyst. He also had a pacemaker fitted at 23 after suffering a complete heart block.
Last year, British schoolboy Lewis Clarke, 16, became the youngest person to trek to the South Pole, accompanied by a guide, Carl Alvey.