Kentucky Route 9 (KY 9) is a state highway maintained by the Kentucky Transportation Cabinet in the U.S. state of Kentucky. The route runs from Newport (a suburb of Cincinnati, Ohio) to Grayson, roughly paralleling the Ohio River between Newport and Vanceburg.

Most of its route, from the Interstate 275 loop at Wilder to Grayson, is also known as the AA Highway (officially, the "John Y. Brown, Jr. AA Highway"). KY 10 forms a branch of the AA Highway between Vanceburg and the Jesse Stuart Memorial Bridge in Grays Branch, near Greenup.

The AA Highway is a rural two-lane highway for most of its length and traverses through some desolate terrain. Driver inattention and speeding, in combination with the numerous side road entrances and at-grade intersections have made it a dangerous and deadly road. To address these issues, guide signs comparable to interstate-styled signs have been installed along the highway at major intersections, along with additional overhead lighting. Other measures to improve safety and increase capacity are under consideration.

The AA Highway was envisioned as a modern highway from Alexandria to Ashland.

Construction began in 1985 on the first segment of the AA Highway. Estimated to cost $266 million to complete, it was designed primarily as a two-lane controlled-access facility. The first phase included the construction of 86 miles (138 km) of the AA Highway from the junction of Interstate 275 and KY 8 in Campbell County east to Vanceburg. The first phase also included the design of two twenty-five mile-long spurs running east from Vanceburg, one ending at US 23 near Lloyd and the Jesse Stuart Memorial Bridge, the other ending near Interstate 64 in Grayson.

When construction began, the costs for the first phase had risen to $292.7 million; the state had sold $300 million in bonds to pay for it. Segments of the highway, from Clarksburg just west of Vanceburg to Tollesboro was routed on an earlier relocated alignment of KY 10.

It officially opened in 1995, however, it was not formally dedicated until 2003.

The AA Highway including the Greenup spur was originally designated as KY 546, and the Grayson spur was signed as KY 694. On May 26, 1988, the designation, "AA Highway," was proposed to be signed along with KY 546 and KY 694. A few years later, this designation was put in place with the AA Highway being co-signed with KY 546 and KY 694, however, many motorists were soon confused by the ever changing designations.

To solve this issue, the AA Highway was renumbered in late-1995. The AA Highway including the Grayson spur was renumbered KY 9, and the Greenup spur was renumbered as KY 10. KY 10 also overlaps portions of the AA Highway throughout the entire highway's existence. Old KY 9 in Campbell county was renumbered as KY 915, and old KY 10 between Vanceburg and South Portsmouth was redesignated as KY 8.

The Kentucky Transportation Cabinet is proposing widening and correcting some deficiencies and addressing growing traffic concerns along the AA Highway from its western terminus near Covington to Maysville. Several options are being considered, such as: removing some of the at-grade intersections, widening to four lanes from two with partial control access, and full control access.

The AA Highway widening study was undertaken. Many residents and users of the road were concerned about intersection safety, while others discussed the high volume of traffic and the lack of passing lanes. Four alternatives were considered:

Two median types were considered: a concrete barrier wall and a depressed grass median. Mountable medians in rural areas are not recommended. With each median type option, there would be 12-foot (3.7 m) travel lanes and 12-foot (3.7 m) shoulders. The depressed grass median would be 40 to 60 feet (18 m), separating the two opposing traffic flows effectively. Due to the high speed of travel, access control with a minimum of 12,000 feet (3,700 m) is recommended for the limited access alternate.