Kreuzlingen is a municipality in the district of Kreuzlingen in the canton of Thurgau in north-eastern Switzerland. It is the seat of the district and is the second largest city of the canton, after Frauenfeld, with a population of about 20,800. Together with the adjoining city of Konstanz just across the border in Germany, Kreuzlingen is part of the largest conurbation on Lake Constance with a population of almost 120,000.