欧洲煤钢共同体（英語：European Coal and Steel Community，簡稱ECSC；法語：Communauté européenne du charbon et de l’acier，簡稱CECA；德語：Europäische Gemeinschaft für Kohle und Stahl，簡稱EGKS）1951年4月18日通过《巴黎条约》成立，1952年7月23日生效。根据条约规定，成员国毋須交纳关税而直接取得煤和钢的生产原料。
|/ / / 欧洲煤钢共同体 (ECSC)|
|TREVI||刑事領域警務與司法合作 (JHA, 欧盟三支柱|
|北大西洋公约组织 (NATO)||[History of NATO]||刑事領域警務與司法合作 (PJCC, 欧盟三支柱)|
|[Western Union Defence Organisation Western_Union_(alliance)#Cannibalisation_and_marginalisation to 北大西洋公约组织]||European Political Co-operation (EPC)||共同外交与安全政策|
|Western Union (alliance) (WU)||/ 西歐聯盟 (WEU)||[西歐聯盟 defined following the WEU's 1984 Rome Declaration 西歐聯盟 to the 欧洲联盟]|
|[Social, cultural tasks History of the Common Security and Defence Policy#1954 – 1970: A dormant WEU is established to 欧洲委员会]||[欧洲委员会]|
- ¹Although not EU treaties per se, these treaties affected the History of the Common Security and Defence Policy of the 共同安全与防务政策, a main part of the CFSP. The Franco-British alliance established by the Dunkirk Treaty was de facto superseded by WU. The CFSP pillar was bolstered by some of the security structures that had been established within the remit of the 1955 布魯塞爾條約 (1948年) (MBT). The Brussels Treaty was 西歐聯盟 in 2011, consequently dissolving the WEU, as the mutual defence clause that the Lisbon Treaty provided for EU was considered to render the WEU superfluous. The EU thus de facto superseded the WEU.
- ²The treaties of Maastricht and Rome form the EU's 歐洲聯盟基本條約, and are also referred to as the Treaty on European Union (TEU) and the Treaty on the Functioning of the European Union (TFEU), respectively. They are amended by secondary treaties.
- ³The 欧洲各共同体 obtained common institutions and a shared 法律主體 (i.e. ability to e.g. sign treaties in their own right).
- ⁴Between the EU's founding in 1993 and consolidation in 2009, the union consisted of 欧盟三支柱, the first of which were the European Communities. The other two pillars consisted of additional areas of cooperation that had been added to the EU's remit.
- ⁵The consolidation meant that the EU inherited the European Communities' 法律主體 and that the 欧盟三支柱, resulting in the EU framework as such covering all policy areas. Executive/legislative power in each area was instead determined by a distribution of competencies between 歐洲聯盟機構 and 欧洲联盟成员国. This distribution, as well as treaty provisions for policy areas in which unanimity is required and Double majority#European Union is possible, reflects the depth of EU integration as well as the EU's partly 超國家主義 (國際關係) and partly 政府間主義 nature.
- ⁶Plans to establish a Treaty establishing the European Political Community (EPC) were shelved following the French failure to ratify the 欧洲防务共同体 (EDC). The EPC would have combined the ECSC and the EDC.