Cablevision Systems Corporation was an American cable television company with systems serving areas surrounding New York City. It was the fifth-largest cable provider and ninth-largest television provider in the United States. Throughout its existence and in its final years, Cablevision serviced customers residing in New York, New Jersey, Connecticut, and a small part of Pennsylvania. However, at one time it did provide service in many as 19 states. Cablevision also offered high-speed Internet connections (Optimum Online), digital cable (Optimum TV/IO Digital Cable), and VoIP (Optimum Voice) phone service (the eighth-largest telephone provider in the U.S.) through its Optimum brand name. Cablevision also offered a WiFi-only mobile phone service dubbed Freewheel.
On June 21, 2016, Cablevision was acquired by European telecom conglomerate Altice.