Wal-Mart Stores Inc. plans to boost pay for its U.S. employees to at least $10 an hour by next year, well above the minimum wage, signaling a tightening labor market and rising competition for lower-paid workers.

The action could signal a turning point for what have been stubbornly stagnant wages since the recession ended almost six years ago, and it would amplify gains for low-wage workers across the nation if other companies follow the nation’s largest private employer. The new rate is 38% higher than the current federal...