Robert Bertie, 1st Duke of Ancaster and Kesteven (20 October 1660 – 26 July 1723) was a British statesman and nobleman.

Bertie was born to Robert Bertie, 3rd Earl of Lindsey and Elizabeth Wharton , and entered Parliament as MP for Boston in 1685. He would serve in that capacity from 1685 until 1687, then would return once again in 1689, but would be forced to leave after inheriting the peerage of Baron Willoughby de Eresby in 1690; he served as Chancellor of the Duchy of Lancaster from 1689 until 1697.

Lord Willougby inherited the Earldom of Lindsey in 1701, and was invested a Privy Counsellor one month later; along with the Earldom of Lindsey, he also inherited the offices of Lord Great Chamberlain and Lord Lieutenant of Lincolnshire, both of which he would hold until his death and would pass onto his son, the 2nd Duke of Ancaster and Kesteven. Lord Lindsey, as he was now styled, was then created Marquess of Lindsey in 1706, and was finally created Duke of Ancaster and Kesteven in 1715 (that year, he also served temporarily as a Lord Justice ). He would die eight years later, an established but relatively unheralded statesman.

|- style="text-align: center;" | width="30%" |Preceded by:
The Earl of Lindsey | width="40%" style="text-align: center;" |Lord Great Chamberlain
1701–1723 | width="30%" |Succeeded by:
The Duke of Ancaster and Kesteven