Benn is MP for Leeds Central and leaves the post of Secretary of State for International Development which he has held since 2003.
Born in 1953, he attended Holland Park comprehensive school and received a degree from the University of Sussex in 1974.
The NFU's president Peter Kendall said: "We are delighted to welcome Hilary Benn to Defra, and look forward to establishing a close and productive working relationship with him and the new Defra team of ministers.
"He comes to Defra at a time when there is a wide-ranging agenda of issues to be resolved. In dealing with all of them, it is vital that he understands the potential that farming offers to provide solutions on issues like food quality and security, climate change, the rural environment and renewable energy.
"With that in mind, we shall be working hard to make sure that agriculture and horticulture remain at the heart of Defra's priorities."