| State: | KY |
| Type: | KY |
| Route: | 109 |
| Map Custom: | yes |
| Map Notes: | KY 109 highlighted in red |
| Length Mi: | 90.309 |
| Length Ref: | [1] |
| Direction A: | North |
| Terminus A: | in rural western Union |
| Junction: | at Sturgis in Providence at Beulah at Dawson Springs in Dawson Springs in Hopkinsville at Hopkinsville |
| Direction B: | South |
| Terminus B: | northeast of Oak Grove |
| Counties: | Christian, Hopkins, Union, Webster |
| Previous Type: | KY |
| Previous Route: | 108 |
| Next Type: | KY |
| Next Route: | 110 |
Kentucky Route 109 (KY 109) is an 90.309adj=midNaNadj=mid north–south state highway that traverses four counties in western Kentucky's Pennyrile region. It traverses Christian, Hopkins, Webster, and Union counties.
KY 109's southern terminus is located in the unincorporated community of Saint Elmo, where it intersects with KY 115 just north of I-24 outside Oak Grove. It joins US 41 on the southeast side of Hopkinsville before that route's interchange with the Pennyrile Parkway (officially designated as I-169). KY 109 runs concurrently with several US and Kentucky routes throughout downtown Hopkinsville before leaving the city and crossing KY 1682 (Hopkinsville Bypass). After its junction with KY 800, it traverses the Pennyrile State Forest; the junction with KY 398 provides access to the Pennyrile Forest State Resort Park. KY 109 traverses more forested areas before entering Hopkins County.
At Dawson Springs, KY 109 has junctions with US 62, where it has a brief concurrency before branching off to traverse an interchange with I-69 (formerly the Western Kentucky Parkway) before exiting the town. It meets KY 70 at Beulah and KY 502 just south of the Webster County line.
KY 109 meets KY 120 and a few other routes in Providence. It continues northwestward into Union County; at Sturgis, it begins a concurrency with U.S. Route 60 (US 60) for a few miles. It branches off from US 60 to traverse the Henshaw community. KY 109 ends at an intersection with KY 56 a few miles east of the bridge over the Ohio River that marks the Illinois–Kentucky state line near Old Shawneetown, Illinois.