Nelson Wilmarth Aldrich (November 6, 1841 - April 16, 1915) was an American politician. He was born in Foster, Rhode Island in 1841. He was elected to the United States House of Representatives in 1879 for a single two-year term, after which he was elected to the United States Senate. He was in the Senate from 1881 to 1911 as an influential Republican.

Aldrich had a major effect on state politics, even before his election to the United States Congress. He served as the president of the Providence city council and Speaker of the Rhode Island House of Representatives, before being elected to Congress. Because of his impact on national politics, he was referred to as the "general manager of the United States".

In 1908, Aldrich introduced a constitutional amendment to establish an income tax, although he had declared it "communistic" a decade earlier. Later, he became the chief sponsor of the National Monetary Commission, later the Federal Reserve. He also served as chairman of the Senate Republican Conference.

Because of his eventual support of an income tax, his daughter Abby Greene Aldrich's marriage to John D. Rockefeller, Jr., and other related reasons, Aldrich is considered to have been one of the most elite politicians at the time, even known as the authentic voice of J. P. Morgan. He died in 1915, four years after his last term in the Senate ended.