The Wentworth by the Sea is a historic grand resort hotel in New Castle, New Hampshire, United States.

In 1905, the hotel housed the Russian and Japanese delegations who concluded the Treaty of Portsmouth to end the Russo-Japanese War.

[1] On July 4, 1964, Emerson and Jane Reed became the first African-Americans to overcome the hotel's segregation policy, dining at its restaurant.

[7] The now-independent Wentworth by the Sea Country Club is home to the golf course that was initially designed by George Wright in 1897, enlarged by Donald Ross in 1921, and further expanded to 18 holes by Geoffrey Cornish in 1964.

While the hotel was vacant, it was used as a haunted setting for the 1999 film, In Dreams, starring Robert Downey, Jr. and Annette Bening.