In Europe, numerous public monopolies in the area of public services have been dissolved. An exception in many countries is the supply of drinking water. This sector is subject to numerous regulations aimed at ensuring supply security, drinking water quality, health protection, and environmental protection. The monopolistic nature of drinking water supply means that antitrust rules regarding the abuse of market dominance also apply. This work elaborates on the details of antitrust oversight concerning water supply companies. While Germany has a specific antitrust provision for water, the legal situation in Switzerland is characterized by the coexistence of antitrust law in the narrower sense and price monitoring law.