Narrowing down the best 38 players from the home unions will have been no easy task, with some tough calls across every position - and the fact of the matter is that there will be some very good players left behind.
However, ahead of the announcement Sky Sports rugby union writer Tony Curtis names his squad for the 10-match tour Down Under.
Remember, you can watch the official announcement live on Sky Sports News on Tuesday at 11am.
The first name on the squad sheet comes in the back-three with Leigh Halfpenny having been in fantastic form during the RBS Six Nations.
The Wales full-back looks nailed on for the No 15 jersey, having moved ahead of Rob Kearney in the pecking order. The Irishman, though, has done nothing wrong and will still prove stiff competition.
The form of Stuart Hogg means he has earned the right to travel with the squad as cover.
Halfpenny is likely to be joined by fellow countrymen George North and Alex Cuthbert, with the trio having linked up to such devastating effect for Wales.
Tommy Bowe could have timed his return to form to perfection, with the Ireland winger a deadly finisher.
For the other wing spot, I would love to see Christian Wade named as a surprise selection. His form for Wasps has been sensational and on the hard, fast pitches Down Under, he could well run riot.
On standby: Sean Maitland's Super Rugby experience and Tim Visser's pace mean they wouldn't look out of place, while Simon Zebo can count himself unlucky not to make it. Chris Ashton endured a Six Nations to forget and played himself out of contention however there is no doubting his talent. Alex Goode and Mike Brown did little wrong for England but they will have to settle for a trip to Argentina in the summer rather than Australia.
Brian O'Driscoll might have come in for some criticism of late, however he still oozes class and his experience will be vital.
O'Driscoll formed a sensational partnership with Jamie Roberts four years ago, and the newly qualified doctor is sure to be part of the squad again.
Wales centre Jonathan Davies has continued to impress alongside Roberts, while the human wrecking ball Manu Tuilagi will give the Australians nightmares.
The last midfield position goes to another wildcard in the shape of Ian Madigan. The Leinster man, who can also add an option at 10, has the running game to take the challenge to Australia.
On standby: Brad Barritt has been England's defensive lynchpin and doesn't get the credit he deserves, while Scotland's Matt Scott impressed during the Six Nations.
Jonathan Sexton and Owen Farrell are destined to be on the flight for Australia - however, who travels as the third fly-half is up for debate.
For me - and despite Gatland's reluctance to pick the players from the Top 14 - it has to be Jonny Wilkinson. He is still performing at the highest level week in, week out, his goalkicking is impeccable and his defence is out of this world. He also still scares the life out of the Wallabies.
Mike Phillips showed glimpses of his 2009 Lions form during the Six Nations and will probably start at scrum-half.
Danny Care would provide the perfect back-up for Phillips, while Greig Laidlaw was outstanding for Scotland and deserves his chance to tour.
On standby: Dan Biggar and Toby Flood will be hoping they have done enough to convince Galtand they are worth their places. Ben Youngs and Conor Murray are unlucky to miss out, with plenty of competition for the No 9 jersey.
There is a wealth of talent for Gatland to look at up front - but the Six Nations-winning trio of Adam Jones, Richard Hibbard and Gethin Jenkins seem to be favourites to tour. Like Wilkinson and Phillips, I would take Jenkins despite his French commitments.
Cian Healy and Dan Cole have earned their places with their form over the past couple of seasons, while Mako Vunipola has played his way into contention, particularly with his ability in the loose.
Rory Best will certainly push Hibbard hard for the No 2 jersey, while Tom Youngs has moved ahead of compatriot Dylan Hartley to provide cover.
On standby: Ryan Grant and Mike Ross have stated strong cases to travel, while Andrew Sheridan has impressed for Toulon. In the battle for the hooker places Richardt Strauss, Ross Ford and Hartley haven't quite done enough to force their way into the squad but will certainly have been in the mix.
Paul O'Connell is back to his best after a long injury absence and should gatecrash the squad. He has the all-round game and is a talismanic figure.
Richie Gray and Joe Launchbury have the running games that will suit the conditions Down Under, while Geoff Parling and Alun Wyn Jones add the grunt and knowhow in the setpiece.
On standby: It is hard on Donnacha Ryan and Ian Evans, who both performed with aplomb during the RBS Six Nations, however they have the ability to step up if needs be. Nathan Hines and Jim Hamilton could also force their way into the reckoning, too, if injuries bite.
The hardest of all the areas of the squad to select - and it is the one area Wales could really dominate.
Sam Warburton, Justin Tipuric and Toby Faletau proved their worth during the Six Nations decider against England in Cardiff, while I would also go for Ryan Jones. He provides useful versatility across the back five and his leadership should not be underestimated.
The explosive power of Sean O'Brien and Jamie Heaslip earn them their places, while Tom Croft's running game and ability in the lineout earns him the final place.
On standby: Chris Robshaw and Kelly Brown just miss out, as do Tom Wood and Peter O'Mahony. Dan Lydiate just hasn't had enough time to prove his fitness but don't be surprised if Steffon Armitage is involved at some point.
Arguably the most crucial of Gatland's decisions. There are a number of candidate who could step into the breach, with Sam Warburton - Gatland's captain during the World Cup and the 2012 Grand Slam-winning campaign - the favourite. However personally I would go for Paul O'Connell. The Ireland and Munster lock leads from the front and has an aura about him when he plays. He has done the job before to great credit and knows what it takes to unify the home unions.