Elections to Welwyn Hatfield Borough Council took place on 6 May 2021. This was on the same day as other local elections across the United Kingdom.
At the previous election the Liberal Democrats managed to gain enough of the popular vote to end the Conservatives majority of the council for the first time since 2002. However, the results saw the Conservatives regaining much of the popular vote at the cost of the Liberal Democrats, with a swing of nearly 10 points. The Conservatives gained five seats, resulting in them once again gaining majority control of the council, with a working majority of eight. The leader of the Conservatives on the council, Tony Kingsbury, assumed the position of leader of the council, and swiftly confirmed a new cabinet portfolio consisting of his fellow Conservative councillors.
Despite a relatively minor drop in the vote share, Labour lost four of their seats. This marked the first time Labour failed to win a seat in a set of Welwyn Hatfield's local elections in the council's history. These loses were also enough for them to have less seats on the council than the Liberal Democrats, meaning for the first time the Liberal Democrats were the official opposition on the council. The Green Party also nearly doubled their share of the vote, although they still finished last in all their contested seats.