|Maintained by FDOT|
|Length:||37.656 mi (60.601 km)|
|South end:||US 1 / US 17 in Jacksonville|
|US 301 in Callahan|
|North end:||US 1 / US 23 / US 301 towards Folkston, GA|
U.S. Highway 23 (US 23) is a United States Numbered Highway that runs from Jacksonville, Florida to Mackinaw City, Michigan. In the U.S. state of Florida, US 23 is concurrent with US 1 south of Alma, Georgia, except in Downtown Jacksonville. US 23 is also concurrent with US 301 between Homeland, Georgia and Callahan. In the Jacksonville area, US 23 is the unsigned State Road 139 (SR 139), which also continues east from the south end of US 23 along SR 10A to SR 115 near the Mathews Bridge.
U.S. Route 23 begins at US 1 (Main Street) at the northern end of downtown Jacksonville, starting as a one-way pair, with the northbound lanes meeting with Florida State College. It is also unsigned SR 139 from its southern terminus to its interchange with US 1 in northwestern Jacksonville (SR 139 continues east along SR 10A from the end of US 23 to SR 115). West of I-95, US 23 ends the one-way pair, continuing as Kings Road through northwestern Jacksonville, as an off-grid road. A few miles to the west, US 23 meets with US 1/SR 15 (Martin Luther King Jr. Parkway), running concurrently with the highway through the rest of its journey through Florida. The road continues northwest, intersecting with Interstate 295 (I-295) and eventually makes its way out of Jacksonville. At Callahan, US 1/US 23 meets US 301, beginning a three-way concurrency as the road continues northward towards the St. Mary's River, leaving Florida and entering Georgia.
US 23 was extended into Florida in about 1950.
|For the rest of SR 139, see SR 10A (mile 1.24-0.000)|
|Duval||Jacksonville||0.000||0.000|| US 1 / US 17 north / SR 228 east (North Main Street / SR 5)
East Union Street (SR 10A east / SR 139 south)
US 90 Alt. west (North Laura Street)
|0.688||1.107||To I‑95 / US 90 (Beaver Street) / North Davis Street|
|0.84||1.35||I‑95 / US 17 south / SR 228 west (SR 9) to I‑10 west||I-95 exits 353B-C; north end of US 17 / SR 228 overlap; no direct access from US 23 south to I-95 north (turn around at North Davis Street)|
|3.820||6.148||US 1 south (M.L. King Jr. Parkway / SR 15) to I‑95||Interchange; no southbound entrance; north end of SR 139 overlap; south end of US 1 / SR 15 overlap|
|See US 1 (mile 511.20-545.03)|
|Nassau||Boulogne||37.656||60.601||US 1 north / US 23 north / US 301 north / SR 4 north / SR 15 north – Folkston, Nahunta, Waycross||Georgia state line (St. Marys River bridge)|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi
|U.S. Route 23|