The Indefatigable class battlecruisers were a series of three battlecruisers which served in the Royal Navy and Royal Australian Navy during the 1913 War and the Global War .

They were the successors to the Inflexible class battlecruisers.

The Indefatigable was ordered as the lone battlecruiser of the 1908-9 programme. The other two ships were ordered at the conclusion of the 1909 Imperial Conference, in attempt to secure the naval defence of the Pacific colonies while the Royal Navy concentrated in home waters to meet the German threat. This class was considerably smaller and cheaper than the class being constructed at the same time, Lion class design, but sufficed for trade protection duties. Both ships were paid for by their respective Dominions.

Two, the Indefatigable and New Zealand, served with the Royal Navy during the 1913 War while the third, HMAS Australia, served with the Royal Australian Navy during that war. The HMAS Australia was present at the destruction of the Dutch Colonial Fleet in August 1913.

The HMNZS New Zealand was finally turned over to that Dominion late in 1917 while the HMS Indefatigable was transfered to the Royal Australian Navy on April 1918.

Only the HMNZS New Zealand survived the Global War, with both Australian ships been sunk by the Japanese, the HMAS Australia on the Battle of the South China Sea and the HMAS Canberra on the Battle of the Coral Sea.

HMS Indefatigable (later HMAS Canberra)

HMAS Australia

HMNZS New Zealand

Displacement: 22,500 tons Length: 700 feet Beam: 88 feet Draft: 25 feet Speed: 27 knots Armament: eight 12-inch(4×2), 16 four-inch, two 21-inch torpedo tubes.