Acarius (died 14 March 642), venerated as Saint Acarius, was a monk of Luxeuil Abbey who became Bishop of Doornik and Noyon, which today are located on either side of the Franco-Belgian border.
Apparently, Acarius had great influence on the spreading of Christianity in Belgic Gaul.
It was Acarius that recommended to Dagobert that Audomar be appointed Bishop of Thérouanne.
Along with Audomar and the King's counselor, Éloi, they were eventually able to persuade Dagobert to allow Amandus to return, and Acarius sent him to preach in the area of Tournai.
As bishop, Acarius was especially attentive to the poor and afflicted, whose needs he enjoyed relieving and calming their suffering.