Middle Fork Kentucky River is a river in Kentucky in the United States. It is a fork of the Kentucky River that it joins just upstream of Beattyville. It is approximately 85 miles (137 km) long.

It rises in the Appalachian Mountains in extreme southeastern Kentucky, in northeastern Harlan County, approximately 5 mi (8 km) from the Virginia state line. It flows initially southwest, in the valley on the eastern side of Pine Mountain, then passes along the southeastern end of the ridge, flowing north through the Cumberland Plateau past Hyden. At Buckhorn, it is impounded to form the Buckhorn Lake reservoir. North of the reservoir it flows generally northwest and joins the North Fork in Lee County.

The Kentucky River basin, including Middle Fork and its tributaries, suffered a major flood in January and February 1957. Peak flood levels were higher by 5.0 feet (1.5 m) at Buckhorn and 2.83 feet (0.86 m) at Tallega than the previous record peak levels in 1939. One person was drowned in Cutshin Creek.

Most of the urban damage was at Buckhorn, with properties under up to 10 feet (3.0 m) of water, and at Hyden. In Bockhorn 10 homes were destroyed, and in Hyden 30% of the homes were damaged in some way. 20 commercial buildings in Hyden were flooded, and the local lumber company had a lot of its stock swept away.

The confluence of Bull Creek, the main Middle Fork, and Cutshin Creek was known in the 19th century in Kentucky as a "turkeyfoot".

The name of Hell-For-Certain Creek comes, anecdotally, from the bad experience of a pair of travellers navigating its waters. It is a common favourite name to use in stories about travelling in Kentucky, although the eye dialect pronunciation of "Hell For Sartin" that is employed by storytellers is incorrect and considered offensive and insulting by native Kentuckyans.

The Osha post office was established by postmaster William C. "Short Buckel Bill" Begley on 1906-09-15. Begley had originally wanted the name Hell For Certain after the creek, but this was rejected by the USPS, so his second choice was the name of his daughter (1893–1990). It was located at the mouth of Hell-for-Certain Creek, and closed in December 1907.

The Omarsville post office was established on 1929-02-27 by postmaster Lilbern W. Woods. It was named after Omar Huff, the son of Republican Party official Elmer Huff. Originally located at the mouth of Mill Branch, it moved around several times over the years. It was at several sites on Big Fork, then in 1942 postmasters Ethel Pilatos (née Woods and Lilbern's sister) and her husband Sam Pilatos (an immigrant from Greece) moved it to the site of Sam's store that, then was and still now is, located at the mouth of Devils Jump and called The Mouth of Devils Jump Branch. Because of other similarly named post offices and mail being misdirected, on 1945-03-01 Omarsville was renamed Kaliopi after Sam's mother (c.f. Calliope). It closed in July 1981.

The Dryhill post office was established on 1897-09-30 by postmaster Dan McDaniel. It was located on a literally dry hill just above the "turkeyfoot" confluence of Bull Creek, Middle Fork, and Cutshin Creek, where the Daniel Boone Parkway and Kentucky Route 257 now cross Middle Fork. Like Omarsville, it served a store located at the mouth of Bull Creek and called The Mouth of Bull Creek. It closed in July 1908, and McDaniel tried to reestablish it on 1910-08-13, this time using his own surname. However, that name was taken in Breckenridge County so he continued with the original Dryhill. It became a rural branch of Hyden post office in 1964.

The Gad post office was established on 1905-03-01 by postmaster Polly Osborne. She had originally wanted the name Bull Creek but that was taken and so she chose Gad after the Tribe of Gad or Gad. It was originally located a slight distance upstream on Henry Fork, and on 1924-05-31 moved to Bull Creek itself at the mouth of Thousandsticks Creek, after which it was at the same time renamed. It closed in November 2004.

Thousandsticks post office, the creek it was renamed after, a school, church, the local weekly newspaper in Hyden, and Thousandsticks Mountain after which they all were named, have two different origin stories for their names. The first is that early settlers found a large number of old dead trees in the area and so named it after the "thousand sticks", i.e. tree trunks. The second is that early travellers discovered the aftermath of a forest fire in the area and so named it after the "thousand sticks", i.e. charred tree stumps.

Kentucky Route 118, which joins the Daniel Boone Parkway at Thousandsticks, is called the "Hyden Spur" as it is the access road for Hyden.

In 1918, Howard Asher and Rene Asher had mines on Red Bird just downstream of the ford that is downstream of Asher Branch. Andrew Asher had one on Banger Branch; and Hughes Asher one on Roberts Branch.

Nathanial Roberts's mine was on Roberts Branch.

• List of rivers of Kentucky