Lucy Clementine Moores Rigby is a British Labour Party politician and solicitor who has been Member of Parliament for Northampton North since 2024 and Economic Secretary to the Treasury since 6 September 2025. She previously served as Solicitor General for England and Wales between 2 December 2024 and 6 September 2025.

Rigby's father served in the Royal Engineers and she was born in RAF Hospital Wegberg in Germany. Her mother worked for the NHS.

Rigby studied politics at Durham University, graduating with a Bachelor of Arts (BA) degree. She then undertook a Graduate Diploma in Law (a law conversion course) at Nottingham Law School and the Legal Practice Course at the Oxford Institute of Legal Practice.

Rigby spent time with the International Criminal Tribunal for the former Yugoslavia in the Hague. She joined Magic Circle law firm Slaughter and May as a trainee in 2007, and was admitted as a solicitor in May 2009. She spent secondments in Brussels and Sydney. She remained at Slaughter and May as an associate from 2009 to 2011, specialising in competition law. She then joined the litigation unit of the Office of Fair Trading, working from 2011 to 2012.

After spending time dedicated to trying to win a parliamentary seat at the 2015 General Election, Rigby then worked at the consumer body Which?, from 2015 to 2017. She specialised in competition and consumer law matters.

In March 2017, Rigby joined the competition specialist law firm Hausfeld & Co LLP. She specialised in competition law. She became a partner in 2021.

Rigby was listed as a 'Global Leader in Competition Plaintiff' in Who's Who Legal 2023 and in Lawdragon's 500 Global Plaintiff Lawyers 2024.

Rigby was a board member of The Collective Redress Lawyers Association from November 2021 to April 2024.