Sister Monica is a nun who visits the Craggy Island Parochial House in the Series 1 finale Grant Unto Him Eternal Rest.  She was portrayed by Irish actress Mairead McKinley.

Ted offers to take her to see the Holy Stone of Clonrichert and after Jack 'dies' she decides to return to her convent but when the solicitor arrives to read the will, in which Jack has left Ted and Dougal £500,000 each, Ted blanks her when she needs help with removing her luggage from the house as she prepares to head to the ferry.