Sister Fidelma is a fictional amateur detective , the eponymous heroine of a series by Irish author Peter Tremayne (pseudonym of Peter Berresford Ellis ).

She is a religieuse of irish-catholic faith, but received also training in both criminal and civil law, especially the brehon laws, being a dalaigh to the Brehon Court of Ireland, attaining the rank of anruth .

She is almost always accompanied by Brother Eadulf, a saxon monk.

The stories are set in the middle of the 7th century, mainly in Ireland. They are historical whodunnits in the literary tradition of Umberto Eco's The Name of the Rose and the Brother Cadfael mysteries by Ellis Peters.

She features in the following books:

• Absolution by Murder
• Shroud for the Archbishop
• Suffer Little children
• The Subtle Serpent
• The Spider's Web
• Valley of the Shadow
• The Monk Who Vanished
• Act of Mercy
• Hemlock at Vespers (short stories)
• Our Lady of Darkness
• Smoke in the Wind
• The Haunted Abbot
• Badgers' Moon
• Whispers of the Dead (short stories)
• Leper's Bell