Walsingham was born in Kent in about 1530. After studying at Cambridge, he went abroad, returning in 1552 to enrol at Gray's Inn. The death of Edward VI saw him once again travelling abroad, this time as a law student at Padua. Only at the accession of Elizabeth I did he return, and was elected MP for Banbury in 1559 and then Lyme Regis in 1563. In the years that followed, he became active in soliciting support for the Huguenots in France among the English clergy, and began to organise the network of spies for which he later became famous. Amongst his spies was Christopher Marlowe, the playwright and intellectual.
In 1570 he was chosen to succeed Sir Henry Norris as amabassador to France by William Cecil, the queen's chief advisor. He made such a success of it that he was entrusted with a more prestigious role, becoming a secretary of state and receiving a knighthood for his efforts. He spent the years between 1578 and 1583 engaged in further diplomatic missions, meanwhile establishing a network of spies throughout Europe. It was Walsingham who was behind the discovery of the Babington plot, which would be the catalyst that brought about the execution of Mary, Queen of Scots in 1587. He was an active participant in her trial.
Although a devoted Protestant and an advisor on whom Elizabeth came to depend during the middle part of her reign, Walsingham received little in the way of material reward from the queen. He died in 1590, leaving considerable financial debt.