| District: | 2nd |
| Predecessor: | Theodore A. Bell |
| Successor: | William Kent |
| State: | California |
| Term: | March 4, 1905 – March 3, 1911 |
| Party: | Republican |
| Birth Date: | 6 October 1862 |
| Birth Place: | Orillia, Ontario, Canada |
| Death Place: | Berkeley, California |
| Occupation: | Attorney, carriage painter |
Duncan E. McKinlay (October 6, 1862 – December 30, 1914) was an American lawyer and politician who served three terms as a U.S. Representative from California from 1905 to 1911.
Born in Orillia, Ontario, Canada, McKinlay attended the common schools. He later learned the trade of carriage painting and worked in Flint, Michigan, and San Francisco, Sacramento, and Santa Rosa, California. After studying law, he was admitted to the bar by the Supreme Court of California in 1892 and commenced practice in Santa Rosa. He served as second assistant United States attorney at San Francisco from 1901–1904, and first assistant United States attorney from 1904–1905.
McKinlay was elected as a Republican to the Fifty-ninth, Sixtieth, and Sixty-first Congresses (March 4, 1905 – March 3, 1911). He was unsuccessful for renomination to Congress in 1910. After McKinlay's defeat, President William Howard Taft appointed him United States surveyor of customs for the port of San Francisco. He died in Berkeley, California on December 30, 1914, and was interred in Sunset View Cemetery in nearby El Cerrito.
McKinlay was an avowed supporter of the Geary Act restricting Chinese immigration. At the Chinese Exclusion Convention in 1901, he led the speakers with the "Legal Aspects of the Chinese Question", lauded by the San Francisco Call as a "brilliant address". He concluded the speech calling for a renewal of the Geary Act which would "guard and protect [us] from the blighting curse of Asiatic immigration".[1]