A modular handgun holster, having a holster assembly with first and second internal longitudinal channels defined by first, second, third, and fourth rail guides respectively. A spacer assembly is positioned within the holster assembly. A belt clip assembly has first and second elongated notches interchangeably mounted onto the first or second internal longitudinal channel of the holster assembly. The belt clip assembly further has a first locking protrusion. A waistband clip assembly has third and fourth elongated notches interchangeably mounted onto the first or second internal longitudinal channel of the holster assembly. The waistband clip assembly further has a second locking protrusion. The holster assembly is symmetrical or approximately symmetrical to snugly receive a handgun.