Zulily is an American e-commerce company. Headquartered in Seattle, Washington, Zulily sells clothing, toys, and home products. Zulily was started in 2009 by Blue Nile executives Mark Vadon and Darrell Cavens. Its initial public offering valued the company at $2.6 billion.

Zulily was founded in 2009 by Mark Vadon and Darrell Cavens after Vadon's wife got pregnant and he was overwhelmed by the supplies they never knew they needed. Zulily went live on January 27, 2010 with an initial focus on children’s apparel. By the fourth quarter of 2010, Zulily was a cash-flow-positive business.

When Zulily went public in November 2013, the company had 2.6 million active customers and $331 million in revenue.

In August 2015, Zulily was purchased by Liberty Interactive's QVC division for $2.6 billion.In September 2017, Zulily launched Private Label Credit Card.

Zulily's target audience is mothers who are on the lookout for unique brands and products for their children; their audience has also been described as "young, tech-savvy mothers". Sales change daily, starting from 6 a.m. Pacific time, and they hold no inventory. In 2014, half of Zulily's orders came from mobile devices. Sales generally last 72 hours.

In 2015, it decreased the number of flash sales, in response to some customers who were overwhelmed by the amount of merchandise from which to select. Retaining customers is a challenge for it: "the flash-sale website is straining to hold on to customers and realizing it may have inundated shoppers with too many deals". Although revenue was up 29% in the first quarter of 2015 compared to the prior year, that was less of a huge increase than the 52% shown for the last quarter of 2014 compared to one year earlier, leading the company to lower its estimate of anticipated revenues in 2015.

Although the web site for the company says they hold no inventory, in 2015 they began to hold some merchandise in warehouses to shorten the time for delivery. The company is including some established brands in addition to the emerging brands on which it had completely relied.