| State: | TX |
| Maint: | TxDOT |
| Type: | RM |
| Route: | 1623 |
| Length Mi: | 23.386 |
| Length Ref: | [1] |
| Length Round: | 3 |
| Map Custom: | yes |
| Formed: | 1951 |
| Direction A: | North |
| Direction B: | East |
| Terminus A: | north of Stonewall[2] |
| Terminus B: | in Blanco |
| Junction: | in Stonewall |
| Counties: | Gillespie, Blanco |
| Previous Type: | FM |
| Previous Route: | 1622 |
| Next Type: | FM |
| Next Route: | 1624 |
Ranch to Market Road 1623 (RM 1623) is a 23.386miles farm to market road in Gillespie and Blanco counties, Texas.
RM 1623 begins in eastern Gillespie County at an intersection with RM 2721. It travels to the south into Stonewall, where it crosses Ranch Road 1, and has a one-block eastward concurrency with US 290 before continuing southward. It then turns to the southeast and crosses into Blanco County. The route intersects RM 1888 before turning to the east and running along the north bank of the Blanco River into Blanco. The RM 1623 designation ends at US 281 in central Blanco; the roadway continues as Loop 163.
FM 1623 was first designated in Blanco County in 1951, and ran from US 281 in Blanco to the west approximately 5miles. Its length was extended to 10.3 mi in 1953 and increased again in 1954; the designation ended at the Gillespie County line. The extension into Gillespie County and to US 290 would be approved in 1955. The route was redesignated in 1969 as an RM route, the same year the extension to RM 2721 was added.