Siward (died 1048) was Abbot of Abingdon in Berkshire (now Oxfordshire) and a bishop in the Diocese of Canterbury.
Eadsige elevated Siward to the rank of bishop, but no mention is made of the title of this bishopric.
Between 1044 and 1048 he was involved in a legal dispute between a noble named Brihtwine and the abbey regarding land held at Leckhampstead.
In the time of King Cnut this land had passed from the abbey to Brihtwine's father Brihtmund for a term of three generations.
As a result of the death some land and personal treasures including the furnishings of his chapel were given to Abingdon Abbey[6]