Siobhán Kate Cullen is an Irish actress. She began her career as a child actress, making her debut in Marina Carr's By the Bog of Cats (1998) at the Abbey Theatre. She landed her first major screen role in Eoin Macken's horror film The Inside (2012).

Cullen had roles in the RTÉ1 and BBC One miniseries Paula (2017), the ITV adaptation of The Long Call (2021), the BritBox series The Dry (2022–2024), the RTÉ series Obituary (2023–), and the Netflix series Bodkin (2024). She was named a 2022 Screen International Star of Tomorrow.