(or Cille, also Cissa), an English abbess, was niece of Cissa, regulus of Wessex in the reign of Kentwin (A.D. 676-685), and sister of Heane, the founder of the monastery at Abingdon. Out of her patrimonial estate she- erected (about 690) a nunnery, which she named after the Holy Cross and St. Helena, at Helenstow, near the Thames, in Berkshire. Cilla presided over her foundation until her death, after which the community removed higher up the Thames, to Witham.