DoorDash will acquire grocery delivery firm Instacart in a $17bn (£12.8bn) deal, creating a behemoth that will bring more meals, quick-need purchases and big weekly shops directly to customers.
DoorDash said the deal, expected to be final in about a year, will expand options for customers and let more sellers use the companies' services.
Instacart shoppers will be able to buy from 150,000 stores, up from the current 100,000, while DoorDash will reach beyond restaurants into retail, the firms said.
"Together, we can accelerate innovation across the grocery industry and make online grocery more seamless and affordable for the millions of households we serve," Instacart's chief executive said.
"Over the last 14 years, Instacart has transformed online grocery by helping retailers of all sizes compete and grow, and joining forces with DoorDash allows us to do even more," CEO Chris Rogers also said.