SAN JOSE, Calif. – In a move that changes the landscape of the highly competitive mobile-computing industry and could spark a wave of blockbuster deals, Google Inc. said Monday that it will pay $12.5 billion to acquire phone maker Motorola Mobility Holdings Inc.

The deal, by far the largest in Google’s history, has been approved by the boards of both companies. It will give the Mountain View, Calif., company its own hardware products and allow it to compete more closely with phone and tablet makers such as Apple Inc., Research In Motion Ltd., Hewlett-Packard Inc. and the new alliance between Microsoft Corp. and Nokia Corp.

The acquisition also gives Google access to more than 17,000 patents held by Motorola, which pioneered the cellphone business. Analysts said that could help Google stave off a barrage of patent claims levied by Apple, Microsoft and other rivals battling the company’s Android operating system.

The deal could also boost Google’s faltering efforts to bring the Internet to living-room television sets by allowing Google to leverage Motorola’s expertise in set-top TV boxes.

Fundamentally, the decision to buy Motorola underscores the growing importance of mobile computing to Google, which draws most of its revenue from selling advertising associated with Internet searches, as consumers and workers increasingly perform more computing tasks with hand-held devices. Google’s lead in mobile search is thought to be even greater than its search dominance on desktop computers.

“It’s no secret that Web usage is increasingly shifting to mobile devices, a trend I expect to continue,” Google CEO Larry Page said in a conference call Monday morning. “With mobility continuing to take center stage in the computing revolution, the combination with Motorola is an extremely important event in Google’s continuing evolution that will drive a lot of improvements in our ability to deliver great user experiences.”

Buying the new company gives Google its own manufacturing operation for the first time. Google had briefly dipped its toes into the business of selling phones by contracting with HTC to build the Nexus phone, using Android software.

If approved by regulators, the Google-Motorola deal could set the stage for a massive battle between five integrated hardware-software platforms: Apple, with iOS; HP, with webOS; Research In Motion’s BlackBerry devices; Nokia phones with Microsoft’s Windows Mobile operating system; and Google’s Motorola phones with Android.

Google said it will pay $40 a share in cash for Motorola Mobility’s stock, a premium 63 percent higher than the stock’s closing value on Friday.