Interstate 40 (I-40) is an Interstate Highway in Oklahoma that runs 331 miles (533 km) across the state from Texas to Arkansas. West of Oklahoma City, it parallels and replaces old U.S. Highway 66 (US-66), and, east of Oklahoma City, it parallels US-62, US-266, and US-64. I-40 is the longest Interstate highway in Oklahoma.

U.S. Route 266 is a 43.09-mile (69.35 km), east–west U.S. Numbered Highway in Okmulgee, McIntosh, and Muskogee counties in Oklahoma, United States, that connects U.S. Route 62 U.S. Route 75 in Henryetta with U.S. Route 64 in Warner. The highway no longer meets the former route of its parent, U.S. Route 66, and is closely paralleled by Interstate 40 (I-40), which replaced US 266 as the major east–west highway east of Oklahoma City during the 1960s.