Which Shark Tank investor co-founded the television network HDNet?

Mark Cuban co-founded the television network HDNet.

Cuban and Philip Garvin launched HDNet in 2001 as a high-definition television network. The service was designed to showcase programming in the then-emerging high-definition format, including sports, concerts, and original content.

The network was later renamed AXS TV after changes in ownership and branding. That later name can cause confusion, because HDNet refers to the network's original identity and early history, while AXS TV is the name used in its subsequent development.

Cuban's involvement with HDNet reflects the media side of his career. Before and alongside Shark Tank, he built businesses in technology, online broadcasting, sports, and television, making him one of the show's most media-focused investors.