Canberra's Ireland wing Hansen and Melbourne's Scottish centre Tuipulotu are set to be key figures in the 38-strong squad that was named on Thursday in a special unveiling event at London's O2 Arena.
England's Itoje will captain the squad that features 21 forwards and 17 backs, with coach Andy Farrell hailing him as "a special person".
The 30-year-old Saracens lock is the first Black player to captain the Lions and only the third Englishman in 89 years to be appointed leader of the touring side.
One of the few sure Test starters, Itoje will be embarking on his third Lions tour after being selected as the youngest player in New Zealand in 2017 and playing a standout role in South Africa in 2021.
He was on the stage with Farrell at the O2 - but there was an anxious wait for the rest of the squad to learn whether they had been selected.
Tuipulotu, the Scottish captain who had missed the whole of the Six Nations with a pectoral inujry, learned the news with three of his Glasgow Warriors colleagues who were also selected.
"To be honest, I'm struggling to speak a bit. I'm just relieved, excited, everything you could imagine ... it's unreal," said Tuipulotu, who led the Scots to victory over the Wallabies last November.
"I've been back in full training for the last couple of weeks, hitting things again and I'm feeling really good. It's either this week or next week that I'll be able to play again."
Winger Hansen is one of Farrell's favourites, having done such a fine job for the Englishman when he was in charge in Dublin.
The Lions have a game against Argentina in Dublin on June 20. They will have five tour games before the first test in Brisbane on July 19. The second and third Tests are on July 26 and August 2.
THE BRITISH AND IRISH LIONS SQUAD FOR THE TOUR OF AUSTRALIA
Forwards
Tadhg Beirne (Munster Rugby/Ireland), Ollie Chessum (Leicester Tigers/England), Jack Conan (Leinster Rugby/Ireland), Luke Cowan-Dickie (Sale Sharks/England), Scott Cummings (Glasgow Warriors/ Scotland), Tom Curry (Sale Sharks/England), Ben Earl (Saracens/England), Zander Fagerson (Glasgow Warriors/Scotland), Tadhg Furlong (Leinster Rugby/Ireland), Ellis Genge (Bristol Bears/England), Maro Itoje (Saracens/England) - Captain, Ronan Kelleher (Leinster Rugby/Ireland), Joe McCarthy (Leinster Rugby/Ireland), Jac Morgan (Ospreys/Wales), Henry Pollock (Northampton Saints/England), Andrew Porter (Leinster Rugby/Ireland), James Ryan (Leinster Rugby/Ireland), Pierre Schoeman (Edinburgh Rugby/Scotland), Dan Sheehan (Leinster Rugby/Ireland), Will Stuart (Bath Rugby/England), Josh van der Flier (Leinster Rugby/Ireland).
Backs
Bundee Aki (Connacht Rugby/Ireland), Elliot Daly (Saracens/England), Tommy Freeman (Northampton Saints/England), Jamison Gibson-Park (Leinster Rugby/Ireland), Mack Hansen (Connacht Rugby/Ireland), Huw Jones (Glasgow Warriors/Scotland), Hugo Keenan (Leinster Rugby/Ireland), Blair Kinghorn (Toulouse/Scotland), James Lowe (Leinster Rugby/Ireland), Alex Mitchell (Northampton Saints/England), Garry Ringrose (Leinster Rugby/Ireland), Finn Russell (Bath Rugby/Scotland), Fin Smith (Northampton Saints/England), Marcus Smith (Harlequins/ England), Sione Tuipulotu (Glasgow Warriors/Scotland), Duhan van der Merwe (Edinburgh Rugby/Scotland), Tomos Williams (Gloucester Rugby/Wales).
With Reuters
