Robert Charles Winthrop (May 12, 1809 – November 16, 1894) was an American lawyer, philanthropist, and Whig Party politician who represented Massachusetts in the United States House and Senate from 1840 to 1851.

After a rapid rise in Massachusetts and national politics and one term as speaker, Winthrop succeeded Webster in the Senate.

Governor George Briggs appointed Winthrop to succeed him, but the 1850 Massachusetts elections resulted in a three-way split of the legislature between Whigs and the Democratic and Free Soil parties, which joined in an anti-Whig coalition.

Winthrop made a final run for public office in November of that year when he stood for governor but was again defeated by the Free Soil-Democratic coalition.

Though he received a plurality of all votes cast, the majority rule in place at the time sent the election to the Massachusetts General Court, where the coalition legislators again denied Winthrop by re-electing Governor George S. Boutwell.

He served as the speaker of the House during the 30th Congress (1847–1849), but could not secure a second term, losing the 1849 speakership election to Howell Cobb in a protracted 63-ballot contest.

[5] Winthrop's views proved no more palatable to abolitionists than did Webster's, and he failed to win reelection by the state legislature to either of Massachusetts' Senate seats in 1851.

Later that year, Winthrop actually won a popular plurality in the race for Massachusetts governor but as the state Constitution required a majority, the election was thrown into the legislature.

[8] With his political career over at the young age of 43, Winthrop spent the remainder of his life in literary, historical, and philanthropic pursuits.

[9] He was a major early patron of the Boston Public Library and president of the Massachusetts Historical Society from 1855 to 1885, during which time he wrote a biography of his ancestor John Winthrop.

She was the daughter of Francis Granger, the postmaster general under President William Henry Harrison and Cornelia Rutsen Van Rensselaer.

[19]His granddaughter, Robert Jr.'s daughter Margaret Tyndal Winthrop (1880–1970),[20] married James Grant Forbes on November 28, 1906.