A touch sensor includes a sensor unit including a plurality of first electrodes in an active area spaced apart from each other, and at least one second electrode, a plurality of sensing channels respectively coupled to one of the first electrodes, and each sensing channel including a reference node having a variable voltage coupled to the at least one second electrode, and a processor configured to receive output signals from the sensing channels, and detect a touch input based on the output signals. The plurality of sensing channels may be configured to supply driving signals to respective first electrodes during a first period, receive sensing signals from respective first electrodes during a second period, and generate the output signals corresponding to the sensing signals received from respective first electrodes based on potentials of the respective reference nodes. A method of driving a touch sensor also is disclosed.