Willerich was the second bishop of Bremen in Germany; or, according to some, the first, his predecessor Willehad being just a missionary in the area, and the diocese set up after his death. He was consecrated in 804 or 805.

He took part in a mission to Denmark

Denmark

Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 in 823, with Ebbo of Rheims and Halitgar

Halitgar

Halitgar was a ninth-century bishop of Cambrai . He is known also as an apostle to the Danes, and the writer of a widely-known penitential.-Life:...

, bishop of Cambrai. It had only a very limited success.