Elsa Britt Madeleine Olefjord Widding (born 24 January 1968 in Gothenburg) is a Swedish politician, energy specialist, author and commentator. She was an advisor to the Swedish government on energy and infrastructure issues, and gained public notice in 2009 for her opposition to the state-run energy company Vattenfall buying out Dutch energy company Nuon due to the financial consequences of the decision which became known as the Nuon affair. Since the 2022 Swedish general election, she has been a member of the Riksdag for the Stockholm County constituency as a member of the Sweden Democrats.