美茵茨（德语：Mainz）是德国莱茵兰-普法尔茨州的首府和最大城市，位于莱茵河左岸，正对美茵河注入莱茵河的入口处。美茵茨是政教古都，在神圣罗马帝国时代，美茵茨大主教身兼帝国七大选帝侯之一，驻跸在此，政治与宗教势力权倾一时。美茵茨拥有一所古老的大学，以活字印刷术的发明人古腾堡为大学命名。目前有多个电视台和广播电台的总部设立在此。美茵茨也是莱茵河流域的狂欢节重镇之一，每年二月，美茵茨、科隆与杜塞道夫的狂欢节最为盛大。邻近美茵茨的重要城市尚有威斯巴登、达姆施塔特和法兰克福等等。

美茵茨与隔岸而对的黑森州首府威斯巴登共同形成「双子城」（双联市），是莱茵-美茵-法兰克福都会区的西端入口，也是莱茵兰和普法兹两地的南北分界城。

Mainz (/maɪnts/; German:[maɪ̯nt͡s]; Latin:Mogontiacum, French:Mayence) is the capital of the state of Rhineland-Palatinate in Germany. It was the capital of the Electorate of Mainz at the time of the Holy Roman Empire. In antiquity Mainz was a Roman fort city which commanded the west bank of the Rhine and formed part of the northernmost frontier of the Roman Empire; it was founded as a military post by the Romans in the late 1st century BC and became the provincial capital of Germania Superior. The city is located on the river Rhine at its confluence with the Main opposite Wiesbaden, in the western part of the Frankfurt Rhine-Main; in the modern age, Frankfurt shares much of its regional importance.