Princess Beatrice completed a two-mile swim and 70-mile mountain bike earlier this week
The 28-year-old royal, who completed a two-mile swim and 70-mile mountain bike this week as part of the Virgin Strive Challenge triathlon, will be joined on the active volcano by Sir Richard Branson and his children Sam, 31, and Holly, 34.
The Princess set up the charity Big Change with the Branson children, who organised the Strive Challenge to raise money for the foundation.
She joined the Bransons for the final triathlon stage of the challenge on Monday and is expected to reach the summit of Etna alongside them later on today.
The 28-year-old royal will run and hike almost 20 miles to the summit of Mount Etna in Sicily today
The Virgin Strive Challenge began at the base of the Matterhorn in Switzerland 30 days ago.
Since then, a team of core participants – including the three Bransons – have hiked through the Alps, cycled the length of Italy and swam across the treacherous Straits of Messina from the mainland to Sicily.
The team, who were joined by around 60 other participants at the different stages, hope to raise £1.5 million for Big Change.
Princess Beatrice with Sam and Holly Branson, the children of Sir Richard Branson
Big Change acts as a catalyst for a number of projects – including How to Thrive and Voice 21 – to accelerate their success and give young people the “necessary tools they need to thrive in life”.
Sir Richard is also set to complete the entire Strive Challenge despite narrowly escaping a near-deadly bike crash less than two weeks before he set off at the beginning of September.
The Princess set up Big Change with the Branson children who organised the Strive Challenge
Speaking at the start of the challenge earlier this month, the 66-year-old said he was “very, very lucky” to escape the accident with cuts, a cracked cheek and a damaged knee.
But he said he was determined to finish the 2000km cycle, hike and swim.
The team are expected to reach the summit of Mount Etna late this afternoon.