McIntyre takes over at the Global Energy Stadium after stepping down from his role with Scottish Championship team Queen of the South.
His appointment comes almost two weeks after Derek Adams was dismissed following a dismal start to the new season.
The 42-year-old McIntyre takes the helm with County rock bottom of the table having lost all of their first five league games.
A statement on County's website read: "Ross County Chairman, Roy MacGregor announced today the appointment of Jim McIntyre as their new manager and Billy Dodds as assistant manager.
"The club also announced [interim boss] Steven Ferguson will continue in his new role as head of youth development.
"Roy MacGregor passed on his sincere thanks to the chairman and directors of Queen of the South football club for their understanding in giving Ross County permission to talk to their former manager to allow formal and swift agreement to join the club."
