The3rd Naval Armaments Supplement Programme (マル3計画, 第三次海軍軍備補充計画,Maru 3 Keikaku, Dai-San-Ji Kaigun Gunbi Hojū Keikaku) otherwise known as the "Circle Three" Plan was the third of four expansion plans of theImperial Japanese Navy between 1930 and the start ofWorld War II.

TheLondon Naval Treaty placed severe restrictions on Japan's naval capabilities vis-a-vis theUnited States Navy and the BritishRoyal Navy in terms of tonnage and numbers ofcapital warships. The response of theImperial Japanese Navy General Staff was to initiate a construction program (Maru-1) to build 39 new warships to the allotted tonnage limits in each of the restricted categories, and to invest in types of warships and weaponry not specifically covered by the provisions of the treaty, such as expansion of theImperial Japanese Navy Air Service to 14 Naval Air Groups^[1]

In 1934, theNaval Ministry submitted its second expansion planMaru-2 to theCabinet, to make up for the shortfall in funding caused by modifications to rectify issues with existing equipment after theTomozuru Incident and IJN 4th Fleet Incident, when it was revealed that the basic designs of many Japanese warships were flawed due to poor construction techniques and instability caused by attempting to mount too much weaponry on too small a displacement hull. In addition, 48 new warships and creation of eight new Naval Air Groups were funded.

By 1937, the term of the London Naval Treaty had expired, and the Japanese government refused overtures to participate in further disarmament negotiations. Instead, a massive third expansion plan was officially ratified by theDiet of Japan in 1937, calling for 66 new combat vessels, centering on two of the newYamato-classbattleships and twoShōkaku-classaircraft carriers, and expansion of the Imperial Japanese Navy Air Service by 14 more Naval Air Groups.

This plan was a multiyear (six year) budget, and allocated a total of 806,549,000Yen was allotted for warship construction and 75,267,000 Yen fornaval aviation. The final three vessels (twoKatori class training cruisers, plusIkino supply ship) were funded under the 1938 Supplementary Estimates.

• Evans, David (1979).Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887-1941. US Naval Institute Press.ISBN 0-87021-192-7.

• 1st Naval Armaments Supplement Programme (Maru 1 Keikaku, 1931)
• 2nd Naval Armaments Supplement Programme (Maru 2 Keikaku, 1934)
• 4th Naval Armaments Supplement Programme (Maru 4 Keikaku, 1939)
• Temporal Naval Armaments Supplement Programme (Maru Rin Keikaku, 1940)
• Rapidly Naval Armaments Supplement Programme (Maru Kyū Keikaku, 1941)
• Additional Naval Armaments Supplement Programme (Maru Tui Keikaku, 1941)
• 5th Naval Armaments Supplement Programme (Maru 5 Keikaku, 1941)
• 6th Naval Armaments Supplement Programme (Maru 6 Keikaku, 1942)
• Modified 5th Naval Armaments Supplement Programme (Kai-Maru 5 Keikaku, 1942)
• Wartime Naval Armaments Supplement Programme (Maru Sen Keikaku, 1944)

• Imperial Japanese Navy
• Military history of Japan

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