Horizontal coordination in local and regional dimensions in Türkiye, as a unitary state governed by a presidential system of government, is mainly implemented among municipalities and unions of municipalities. The main typical instance of horizontal coordination at the local and regional level in Türkiye is the horizontal relations between municipalities. The candidacy status of Türkiye for full membership to the EU and accession negotiations enhanced cross-border cooperation and horizontal coordination among local governments with the European partners as well. Municipality unions in different regions serve as platforms to establish collaboration among mayors and council members elected from different political parties. The unions of municipalities in Türkiye carry on activities in various areas such as migration and social cohesion, environment, urbanization, and local economic development. Above all these regional municipality unions, The Union of Municipalities of Türkiye (UMT) is serving as an umbrella organization. UMT mainly aims to defend the common interests of the municipalities and to improve municipalism and also to represent the municipalities at the national and international level. The main power of the UMT is its competence for lobbying to influence the central-level decision making on issues related to the municipalities and filing lawsuits on behalf of municipalities.