AGL Energy is owned by a mix of institutional investors, retail shareholders, private companies, and insiders. The largest single shareholder is Mike Cannon-Brookes through his private investment company Grok Ventures, which owns about 11% of the company. Other major institutional shareholders include State Street Global Advisors (around 8.1%), Franklin Resources, and The Vanguard Group, each holding smaller but significant stakes. Overall, institutional investors hold around 40% of the shares, with retail investors making up about 60% of the shareholders by number though controlling a smaller portion of shares. Insider ownership (directors and management) is minimal at around 0.1%.

Mike Cannon-Brookes has been influential as an activist investor, pushing for AGL to accelerate its transition to carbon neutrality and renewables. He partnered with Brookfield Asset Management in a bid to acquire AGL for a large-scale green energy transition plan, which reflects his significant influence on AGL's ownership and strategy.

In summary, AGL Energy is publicly owned by a combination of institutional investors, retail shareholders, and private investors, with Mike Cannon- Brookes being the largest known individual shareholder.