Lockheed Martin Corp. on Tuesday said it has unloaded $2.6 billion in pension obligations to insurance companies in December, the latest company to deploy a tactic that helps reduce corporate balance sheet exposure to market swings.

Companies record their expected pension-plan obligations and the value of their pension-plan assets on their books, opening themselves up to the risk that a drop in stocks or bond yields could ding their earnings. That risk can be substantial: Lockheed had projected pension benefit obligations of $48.6 billion and plan assets worth $32.9 billion in 2017, according to latest data available.

The world’s largest defense contractor transferred $1.8 billion of its defined-benefit pension obligations to Prudential Financial Inc.’s Prudential Insurance Company of America, the insurer said Tuesday. Lockheed purchased a group annuity contract which covers roughly 32,000 of its retirees.

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Lockheed also struck an $800 million pension risk-transfer deal with Athene Holding Ltd., that requires the insurance company to reimburse Lockheed’s pension trust fund for all future benefit payments made to roughly 9,000 U.S. retirees and beneficiaries.

The two transactions will insulate the company from all volatility associated with $2.5 billion in current pension obligations, and the company will save $25 million a year on its pension insurance fees, Chief Financial Officer Bruce Tanner told investors and analysts on the company’s earnings call Tuesday.

“We think this creates a win-win situation, providing the same benefits to retirees going forward, while reducing future volatility for the business and our customers,” Mr. Tanner said.

Lockheed joins a string of other companies including International Paper Co., FedEx Corp. and Bristol-Myers Squibb Co. that chose to transfer their pension plan liabilities from their balance sheets.

There were approximately 38 pension risk transfers worth through mid-November 2018, according to Pensions & Investments’ Research Center. Of those that reported assets, a total $31.7 billion was transferred in 2018, up from $20.2 billion in 2017 but less than the $60.1 billion in transfers recorded in 2014.

“There has been a recognition of the challenges and risks that companies face associated with maintaining a pension plan,” said Scott Kaplan, head of pension risk transfer at Prudential.

Those risks stem from how companies account for their pension-plan liabilities. Pensions obligations are recorded on the corporate balance sheet as a liability, while the value of the pension plan’s assets offsets that figure. Shifts in stock prices and interest rates impact the value of the plan’s investments, among other factors, and can translate to changes in the size of the company’s unfunded pension obligation.

December’s stock market plunge, which coincided with a drop in interest rates, threatens to hurt earnings of companies with large pension obligations because they may report pension losses or smaller pension gains than previously expected.

“In the fourth quarter, we saw the re-emergence of volatility in the equity market and that has a direct correspondence to the volatility of pension plan funded status,” said Beth Ashmore, a senior consultant focused on retirement with consulting firm Willis Towers Watson PLC. “Now, there’s even more of an awareness of the influence of that risk on the balance sheet.”

Goldman Sachs Asset Management estimates that the funded status among defined-benefit pension plans of S&P 500 companies slumped to an aggregate 85% funded status in December, from a high of 91% funded notched in September.

Companies also are making the move to avoid paying rising insurance premiums to the Pension Benefit Guaranty Corp., the federal pension insurer. Lockheed will save roughly $25 million a year on its PBGC fees.

A spokeswoman from Bristol-Myers Squibb confirmed that the company in December said it will transfer $3.8 billion of its U.S. pension obligation through a termination of its pension plan.

A spokesman from International Paper didn’t respond to requests for comment. Representatives from FedEx didn’t immediately respond to a request for comment.

Write to Tatyana Shumsky at tatyana.shumsky@wsj.com