Robert Todd Lincoln, American lawyer and politician, 35th United States Secretary of War, son of Abraham Lincoln (born 1843)

Robert Todd Lincoln was an American lawyer and businessman. The eldest son of President Abraham Lincoln and Mary Todd Lincoln, he was the only one of their four children to survive past the teenage years and also the only one to outlive both his parents. Robert Lincoln became a business lawyer and company president, and served as both United States Secretary of War (1881–1885) and the U.S. Ambassador to Great Britain (1889–1893).

The secretary of war was a member of the U.S. president's Cabinet, beginning with George Washington's administration. A similar position, called either "Secretary at War" or "Secretary of War", had been appointed to serve the Congress of the Confederation under the Articles of Confederation between 1781 and 1789. Benjamin Lincoln and later Henry Knox held the position. When Washington was inaugurated as the first President under the Constitution, he appointed Knox to continue serving as Secretary of War.

Abraham Lincoln was the 16th president of the United States, serving from 1861 until his assassination in 1865. He led the United States through the American Civil War, defeating the Confederate States of America and playing a major role in the abolition of slavery.