The 27-year-old left-hander from Queensland has agreed a two-year playing contract and succeeds Kevin Curran as captain with wicketkeeper David Ripley as his deputy.
Hayden, who made the last of his seven Test appearances for Australia in South Africa nearly two years ago, had a successful season on the County circuit with Hampshire in 1997.
He scored 2,426 runs in all competitions, including 1,438 in the Championship with four centuries.
Speaking from his home in Brisbane, Hayden said: "I'm very excited about this. I enjoyed my summer with Hampshire and I just hope I can make a really good fist of it for Northants.
"Obviously there's a whole new set-up at the club, with my appointment a part of that, and I'm looking forward to meeting up with all the players when I arrive in April."
Ripley, who made his debut for Northants in 1984, becomes the club's first officially appointed vice-captain since Alan Fordham in 1996.Reuse content