How many years do you have to go to college to become an FBI Agent?

Aspiring FBI agents must possess a bachelor's degree (a four-year degree) from a university or college that is accredited by the U.S. Secretary of Education. Generally speaking, it takes four years to complete a bachelor's degree. That being said, some students take less than four years to complete their degree while other students take longer than four years. According to their website, the FBI does not favor one program of study over another. However, if a student wanted to pursue a career with the FBI it would behoove them complete a degree in a field of study that would help them with their work with the Bureau.
Besides having a bachelor's degree, FBI agents must also have the following:
1. A valid U.S. driver's license.
2. At least three years of relevant work experience.
3. Be at least 23 years of age, but less than 37 years of age at the time of their appointment.
4. Be a U.S. citizens, or a resident of the Northern Mariana Islands.
https://www.fbiagentedu.org/fbi-requirements/