Skarsgard in South Pole challenge
The Hollywood actor has joined a US group taking part in the charitable expedition that has set teams of servicemen and women with physical and mental injuries the challenge of crossing the Antarctic plateau first.
He will be up against a UK contingent featuring Harry and another from the Commonwealth that Dominic has joined.
Speaking about joining the Walking With The Wounded South Pole Allied Challenge, Alex said: "I'm honoured to be working and training alongside these soldiers to raise money and awareness for this very worthy cause."
The three teams will represent charities from the UK, US and Commonwealth and will race just over 200 miles across the frozen wasteland during November and December.
Harry, who took part in the Walking With The Wounded trek to the North Pole in 2011, is already patron of the Antarctica expedition, and confirmed in April he will be taking part with Team UK - also known as Team Glenfiddich - for the whole race.
He missed out on a bid to conquer Mount Everest with the group last year because of his military commitments and he withdrew early from the successful North Pole expedition to attend his brother's wedding.