The 28-year-old took just 18 days to reach the South Pole through a combination of kite-assisted skiing, biking and cross-country skiing.
During the expedition, Skelton set a new Guinness World Record for the fastest 100km by kite ski (7 hours and 28 minutes) and became the first person ever to cycle part of their way to the pole.
"This has been a massive adventure and at times it felt like it was never going to end," she said at the end of her journey. "My body hurts in so many different places, mentally I'm exhausted and I've only washed once in the last 30 days, so to be finally standing at the pole feels incredible.
"I've seen how Sport Relief money makes a big difference and that's why I can't complain about any part of this because it's nothing compared to what some people go through every day of their lives."
Skelton battled severe snow storms and temperatures as low as -48 degrees Celsius on the adventure. She also suffered from numerous blisters, a hacking cough, stomach problems and dehydration at various stages.
Sir Ranulph Fiennes - named by the Guinness Book of World Records as the world's greatest living explorer - was one of the first to congratulate Skelton on her success.
"I have to admit when she first told me that she was going to cycle part of the way to the South Pole, I laughed," he said.
"But through pure grit and determination she has got there and shown that yes you can use a bike to reach the Pole. Her incredible efforts are a great example of willpower."
Skelton previously completed a record-breaking kayaking trip down the Amazon in 2010 and last year became the first person to high-wire walk between the chimneys of Battersea Power Station in London.
Skelton's journey to the South Pole will be documented in an nine-week series on Blue Peter starting tomorrow (January 23).
> Helen Skelton spends Christmas in Antarctica for Sport Relief
Watch Helen Skelton discuss her Antarctic trek below: