Multiprotocol multicast streaming proxy techniques are described. In one or more implementations, a response is sent by a proxy service for receipt by a client device responsive to receipt of a request from the client device to obtain streaming data from a service provider via a network. The response indicates how the client device is to access a multicast of the streaming data from the proxy service and a single dedicated stream of the streaming data. Responsive to receipt of a request from the client device to receive the multicast, the streaming data is obtained by the proxy service via a single dedicated stream from the service provider and multicast for receipt by at least the client device.