W. W. Grainger, Inc. is a Fortune 500 industrial supply company founded in 1927 in Chicago. Grainger serves more than 3 million customers worldwide with offerings such as motors, lighting, material handling, fasteners, plumbing, tools, and safety supplies, along with services like inventory management and technical support. Revenue is generally from business-to-business sales rather than retail sales. Grainger serves its over 3 million customers through a network of approximately 598 branches, online channels (such as Grainger.com, KeepStock and eProcurement), and its robust supply chain including 33 distribution centers.

The company was founded by William Wallace Grainger in 1927 in Chicago, Illinois. He established the company to provide supplies for businesses. The business was incorporated as W. W. Grainger, Inc., in 1928. Sales in the early days were generated primarily through mail order via post cards and a catalog. The MotorBook, as the catalog was originally called, was the basis for today's Grainger catalog. Grainger headquarters are now located in Lake Forest, Illinois. By 1936 Grainger had established 15 branches to improve customer service.

In 1967, Grainger became a publicly traded company. Grainger is a profitable corporation and has increased dividends to its shareholders for forty five consecutive years. The company has grown consistently since becoming public and passed US$10 billion in annual sales in 2016.

In 1996, Grainger launched its first website. The website was a simple page which linked to an electronic catalog. Since that time Grainger.com has evolved into a robust eCommerce platform. In 2016, Grainger was named the 11th largest eCommerce retailer in North America by Internet Retailer. As businesses continued to shift from ordering through traditional channels, such as using phones or visiting branches, to online and onsite channels including websites, eProcurement platforms and inventory management systems, Grainger evolved. In 2016, more than 65 percent of Grainger orders originated via a digital channel (including Grainger.com, inventory management systems, and eProcurement) and more than 85 percent of orders were shipped directly to the customer or made immediately available through onsite services. In 2016, more than 50% of total company revenue was from a digital channel.

While Grainger.com serves primarily large and medium customers in the U.S., Grainger's Zoro U.S. brand was launched in 2011 to serve the small business market in the region through a web-only transaction-based model. Grainger has a similar online-only, or single channel, offer in Japan, through a joint venture called MonotaRO.

Grainger was named by Fortune magazine as one of the top 100 companies to work for in 2013, citing the company's generous profit-sharing plan, where employees with five years of service had 20% of their pay added to their retirement plan.