A sanitary undergarment, comprising a fabric body, a crotch portion, a waist opening, and a thigh opening, each comprising one or more layers made of a breathable leak-proof material for blocking flow of the body fluid through the fabric body. The sanitary undergarment generally comprises a boxer brief construction. The fabric body constitutes a front portion and a rear portion and blocks flow of the body fluid of the wearer outside the sanitary undergarment and prevents staining of the outer garment. The front portion covers a front part of a pelvic region of the wearer. The rear portion covers a rear part of the pelvic region of the wearer. The crotch portion covers a crotch region of the wearer and comprises one or more of a first layer and a second layer. The second layer prevents chafing at the inner thigh regions of the wearer.