Chesterfield caretaker manager Tommy Wright has described the signing of Luis Boa Morte as a "fantastic coup" for the club.
The 35-year-old former Arsenal and Fulham forward has agreed to join the League Two side until January.
"To have a player of Luis's quality coming to Chesterfield is a fantastic coup for us. It's great that a player of his ability wants to play football," Wright told Chesterfield's official website.
"The financial aspect of the deal was no worry - he just wanted to come and play."
Boa Morte played for Arsenal, Southampton, Fulham and West Ham United during a 15-year spell in England.
