The Tri-Nations captain of 2011 has penned a new two-year agreement, taking him through until the end of the 2015 Rugby World Cup.
Horwill spent much of 2012 on the sidelines but after coming through the frustrating period he is now eyeing Warren Gatland's men.
"I'm happy to have my future resolved," Horwill says.
"It was always my intention to remain in Australia. I've still got a lot more that I want to achieve with both the Wallabies and the Queensland Reds.
"Obviously it (the injuries) has been frustrating at times, but you have to take the bad with the good," Horwill says.
"The main thing is to focus on what's dead ahead - and that couldn't be more exciting. Playing the British & Irish Lions is a once in a lifetime opportunity and you can feel the excitement around the country: be it the players, the rugby community or the general public.
"It's coming up quickly now and you can really feel that in the intensity it has brought to Super Rugby this year, especially in the derby games. The competition just to make the squad is fierce, which is exactly as it should be.
"It bodes well for what is going to be the series of a lifetime, both for the Test players but also those players who feature against the Lions in the tour matches. You just have to look at the power in the touring squad they have named to see that."
Horwill is just the latest Wallabies star to sign on with the ARU, following in the footsteps of Scott Higginbotham.
And Robbie Deans reckons the duo's new deals is a major fillip for Australian rugby and sends the right message to out of contract players.
"Players have choices and a lot of factors come into it," added Deans.
"But a playing career is a finite thing so commitments aren't made lightly.
"The key is that these guys see the opportunity ahead, see the progress that is being made in the game in Australia, and want to play their part in continuing to bring it forward."
Horwill has not featured in the Wallaby jersey since the 24-18 win over Wales in Cardiff at the end of 2011, having been ruled out of last year with a ruptured hamstring.
The long road to recovery saw a delayed start to the Super Rugby season, but Horwill responded once he returned, confirming his leadership credentials as the Test season approaches.
He is now aiming to re-enter the Test arena back at Suncorp Stadium when the British & Irish Lions Test series kicks off on June 22.