The present invention relates to an integrated high-voltage battery housing. More particularly, it relates to an integrated high-voltage battery housing adapted to secure safety against side impact collisions while reducing the weight of a vehicle by integrating a connecting structure between a battery housing and a side member of a chassis of the vehicle. In particular, the integrated high-voltage battery housing includes: a bottom housing configured to receive a battery; a battery fixing bracket configured to fix the battery to a top surface of the bottom housing; and a plurality of flanges extending from an upper end edge of a side wall of the bottom housing and each having a coupling aperture for coupling the flange to a chassis side member. A protruding reinforcing portion extends transversely between opposite sides of the bottom housing on a bottom surface of the bottom housing.