Dame Lucy Morgan Theis DBE KC (born 6 November 1960), styled The Hon.

[3] Between 2005 and 2010 she was the head of Field Court Chambers in London and was Chair of the Family Law Bar Association in 2008 until 2009.

Theis was appointed to be a High Court Judge in 2010 and in 2011 she was appointed a Family Division Liaison Judge on the South Eastern Circuit, in this role There had responsibility for Kent, Surrey and Sussex and later for London and Thames Valley.

[3] Mrs Justice Theis was appointed as the Senior Family Liaison Judge for a four-year period from October 2018.

[3] In August 2022, Theis heard one of the cases regarding Archie Battersbee and the withdrawal of his life support.