A treaty of friendship, also known as a friendship treaty, is a common generic name for any treaty establishing close ties between countries. Friendship treaties have been used for agreements about use and development of resources, territorial integrity, access to harbours, trading lanes and fisheries, and promises of cooperation. Whilst not common, there are some treaties agreeing to some forms of military alliance which have use friendship terminology in their titles,^[1] as well as some non-aggression pacts. Additionally, friendship treaties have also signalled an independent relationship with emerging states.^[2]

Ancient Greeks distinguished between three different types of friendships between two polities: Philiai, symmachia, and epimachia. Both symmachia and epimachia were types of alliances, with the former committing States to support each other in battle and the latter requiring parties to assist each other if one suffered an invasion. Philiai, then, made the important distinction of denoting friendship between polities but did not give the treaty partners the status of allies. Romans had a similar word amicitia, which was a state of diplomatic relations which could coexist with an alliance, or exist without it. The Romans employed a practice of establishing peace and friendship with polities on its peripheries, though in practice these relationships were usually built on unequal treaties, requiring the neighbour to support Rome militarily, though not necessarily the reverse.^[1]

In most cases, the friendship treaties are not based on equal partnership. This is particularly the case in treaties between aboriginal nations and the colonizers, both in America and in the Pacific, throughout the Colonial era. These treaties, often written primarily in the language of the coloniser, manipulated the terminology of friendship by the larger powers in order to create an environment of trust, primarily for the benefit of themselves. While promising protection in return for these benefits, the treaties are more subtle ways of accessing resources for commercial exploitation of smaller nations.^[1]

Since the early 2000s, friendship in international relations has been under closer analysis. Whilst friendship terminology had always been used in discourse and diplomacy, the analysis of friendship in international relations had been dismissed as merely being synonymous with good relations. In 2007, Felix Berenskoetter called for the inclusion of friendship analysis into international relations and since then a modest body of literature around the concept has been formed.^[3][4]

• Treaty
• Commercial treaty
• List of treaties