F5 Networks, Inc. (NASDAQ: FFIV) is a networking appliances company. It is headquartered in Seattle, Washington and has development and marketing offices worldwide. It originally manufactured and sold some of the very first load balancing products. In 2010, F5 Networks featured in Fortune's 100 Fastest-Growing Companies list.

F5 Networks' flagship product, the BIG-IP network appliance, was originally a network load balancer but today also offers other functionality such as access control and application security. Add-on modules to F5's BIG-IP family of products offer email filtering and intelligent compression to allow for lower bandwidth and faster downloads in addition to load balancing and local traffic management capabilities.

F5 offers products in various segments of the Application Delivery Controller market. According to Gartner, F5 has "a continued market-leading position" in the Application Delivery Controller market. Gartner cites the most significant competitors (in terms of market share) as Cisco Systems and Citrix Systems. Other competitors include A10 Networks, Armorlogic, Array Networks, Barracuda Networks, Brocade, Coyote Point Systems, Crescendo Networks, KEMP Technologies, Radware and Zeus Technology.