De Lancey Nicoll (June 24, 1854 Shelter Island, Suffolk County, New York - March 31, 1931 Manhattan, New York City) was a New York County District Attorney.
De Lancey Nicoll was born on Shelter Island to Solomon Townsend Nicoll and Charlotte Anne Nicoll in 1854. He attended St.Paul's Schools in Concord, New Hampshire; and graduated from Princeton University in 1874, and from Columbia Law School in 1876.
After serving in private practice, he was appointed in 1885 Assistant New York County District Attorney by D.A. Randolph B. Martine. In November 1887, he ran on the Citizens Reform, Republican and Irving Hall (a faction of Anti-Tammany Democrats) tickets to succeed Martine as D.A., but was defeated by his fellow Assistant D.A. John R. Fellows who ran on the Tammany Hall/County Democracy (the larger faction of Anti-Tammany Democrats) ticket. Upon taking office in January 1888, Fellows dismissed Nicoll from the office of Assistant D.A.
In November 1890, Nicoll ran on the Tammany Hall ticket to succeed Fellows as D.A., and was elected. On December 11, he married Maud Churchill, and their children were De Lancey Nicoll Jr. (1892-1957) and Josephine (1894-1915). Nicoll was D.A. from January 1891 until the end of 1893.
Afterwards he resumed the practice of law. In 1896 Nicoll was among the Democrats who repudiated William Jennings Bryan and campaigned for Republican William McKinley. In 1904, he was chosen by Chairman Thomas Taggart Vice Chairman of the Democratic National Committee.