Reformer could refer to the following:

• A reformer is a person who wishes to change a system to improve it (see Reform movement).
• A reformer is an influential person in the Protestant Reformation (see Protestant reformers).
• A reformer is a personality type in Enneagram spiritual psychology - see reformer (Enneagram)
• A hydrogen reformer is a device that extracts hydrogen from other fuels, typically methanol or gasoline
• A Pilates reformer is an exercise machine used in the fitness discipline Pilates