Nicholas I (Latin: Nicolaus, Danish: Niels, German: Nikolaus) (died 1233[1]) was Bishop of Schleswig between 1209 and 1233.
[1] After Bishop Valdemar Knudsen, also Prince-Archbishop elect of Bremen, son of the murdered King Canute V of Denmark and therefore claiming the Danish throne, had attempted to overthrow King Canute VI of Denmark, the latter captured Bishop Valdemar in 1193, who stayed in royal captivity until 1206.
[1] Canute VI then unilaterally appointed Nicholas as bishop of Schleswig, however Pope Celestine III refused to depose the imprisoned Valdemar.
[2] A delegation sent to the new Pope Innocent III in order to get Nicholas' papal confirmation as bishop, returned with empty hands.
[2][4] In the same year Nicholas followed King Valdemar II in his campaign to conquer the Estonian island Øsel (Saaremaa).