Miguel Ángel Félix Gallardo -- the Mexican drug kingpin who founded the Guadalajara Cartel -- has died at 80.

Félix Gallardo -- who was known as "El Jefe de Jefes" AKA "The Boss of Bosses" -- passed away Sunday in a hospital ... Mexico's Ministry of Security told Milenio.

While no official cause of death is confirmed ... the outlet claimed he suffered multiple organ failures after he was rushed to the hospital from his Puente Grande prison.

The transfer went down with heavy security too ... with air support and assistance from Jalisco State Police and Penitentiary Police.

Félix Gallardo had been sentenced in 1989 to two consecutive prison sentences -- one for 40 years for drug trafficking, weapons stockpiling, and bribery.

The other was for 37 years, which he received after being convicted for the murder of DEA agent Enrique "Kiki" Camarena.

In pop culture, Félix Gallardo was portrayed by Diego Luna in "Narcos: Mexico."