Simpson has played 37 NRL games since making his debut against the Warriors in 2008, and has been a valuable member of the Rabbitohs squad both on and off the field.
Simpson is excited about his new contract at Huddersfield.
“I’m really looking forward to heading to the Huddersfield Giants and starting the next phase of my football career,” Simpson said.
“It’s a great opportunity for me to play Rugby League in other countries and experience the rest of world.
“I’m grateful to the Rabbitohs for the opportunities they’ve given me over the past three seasons both on and off the field.