Robert Charles Winthrop (May 12, 1809–November 16, 1894) was an American statesman who served in the United States House of Representatives and the United States Senate. He was born in Boston, Massachusetts and graduated from Harvard University in 1828.

After studying law with Daniel Webster he was admitted to the bar in 1831 and practiced in Boston. He served in the Massachusetts House of Representatives from 1835 to 1840, and served as Speaker of the House of that body from 1838 to 1840.

Winthrop was elected as a Whig to the 26th United States Congress to fill the vacancy caused by the resignation of Abbott Lawrence; was reelected to the 27th Congress and served from November 9, 1840, to May 25, 1842, when he resigned; subsequently elected to the 27th Congress to fill the vacancy caused by the resignation of his successor, Nathan Appleton ; reelected to the 28th and to the three succeeding Congresses and served from November 29, 1842, to July 30, 1850, when he again resigned to become a Senator.

He was a Speaker of the United States House of Representatives during the 30th Congress; appointed as a Whig to the United States Senate on July 27, 1850, to fill the vacancy caused by the resignation of Daniel Webster and served from July 30, 1850, to February 1, 1851, when a successor was elected; unsuccessful candidate for election to the vacancy in 1851; was an unsuccessful candidate for governor of Massachusetts the same year; presidential elector on the Whig ticket in 1852.

Winthrop engaged in literary, historical, and philanthropic pursuits until he died in Boston in 1894. He was interred in Mount Auburn Cemetery, Cambridge, Massachusetts.

Winthrop is the great-great-grandfather of United States Senator and 2004 Presidential candidate John Kerry.