Two health-insurance mergers worth a combined $82 billion are unraveling in the wake of court rulings that found the transactions violated federal antitrust law, all but quashing a deal boom that would have reshaped the industry.

Aetna Inc. and Humana Inc. said Tuesday they would terminate their $34 billion merger agreement instead of attempting to appeal a judge’s decision last month that their combination would harm senior citizens.

Just hours later, Cigna Corp. said it was calling off its $48 billion merger agreement with Anthem Inc. and pursuing litigation seeking a $1.85 billion breakup fee plus more than $13 billion in damages from its deal partner.

Cigna’s announcement escalated a monthslong fight in which the two companies have accused each other of violating their merger agreement. Anthem immediately disputed Cigna’s authority to nix the deal.

“Anthem will continue to enforce its rights under the merger agreement and remains committed to closing the transaction,” an Anthem spokeswoman said.