SEATTLE — Amazon and Whole Foods Market are introducing free two-hour delivery of groceries from Whole Foods Market to customers with an Amazon Prime membership in Austin, Cincinnati, Dallas and Virginia Beach. The companies plan to expand the service across the United States in 2018.

Customers with a Prime membership may shop thousands of items across the categories of produce, bakery, dairy, meat and seafood and everyday staples from Whole Foods Market at primenow.com or through the Prime Now app. Prime members receive free two-hour delivery or delivery within an hour for $7.99 on orders of $35 or more.

Digital collided with brick and mortar last August when Amazon finalized its $13.7 billion acquisition of Whole Foods Market. That same day, Whole Foods Market lowered the prices of some best-selling grocery staples across its stores. Since then, the companies have introduced Amazon lockers in Whole Foods Market stores. Customers may have products shipped from Amazon.com to a local Whole Foods store for pickup, or consumers may send returns back to Amazon via the lockers.

“We’re happy to bring our customers the convenience of free two-hour delivery through Prime Now and access to thousands of natural and organic groceries and locally sourced favorites,” said John Mackey, co-founder and chief executive officer of Whole Foods Market. “Together, we have already lowered prices on many items, and this offering makes Prime customers’ lives even easier.”