Sinclair Broadcast Group said Friday that it had agreed to acquire 21 regional sports networks from Walt Disney Company in a deal worth $10.6 billion, giving the largest operator of local television stations in the United States a foothold in the cable industry with the rights to broadcast games of dozens of professional teams.

Disney was forced to sell the networks to receive antitrust approval for its $71.3 billion acquisition of most of Rupert Murdoch’s 21st Century Fox in a deal that closed in March. The Justice Department required the sale of the networks, which were part of Fox, because Disney, through its ownership of ESPN, already dominates the market for televised sports.

One of the 22 sports properties that Disney was required to sell, the YES Network, is being acquired by the New York Yankees and the e-commerce giant Amazon for about $3.5 billion, according to people familiar with the transaction. Sinclair also has a stake in that deal.

Disney is getting less for the sports networks than some analysts had expected. Last year, Guggenheim Securities estimated that, including the YES Network, the channels had a value of $22 billion. Regional sports networks have lost value in recent years as fewer people pay for television.