International Boundary Marker, International border marker near Deadwood, Texas, US.

The International Boundary Marker, also called the Republic of Texas Granite Marker, is a granite shaft set where Texas Farm to Market Road 31 meets Louisiana Highway 765, southeast of Deadwood, Texas. It stands on a three-acre parcel split between DeSoto Parish, Louisiana, and Panola County, Texas, near the Toledo Bend Reservoir.

The marker was created in 1840 and placed in 1841 to define the boundary when Texas was still an independent nation. It remains a physical record of that territorial separation.

The granite marker is also called the Republic of Texas Granite Marker, a name recalling the years when Texas was an independent republic. Its survival is tied to the 1840–1841 survey team, who worked through swampy conditions and funding gaps. In 1980 the Texas and Louisiana sections of the American Society of Civil Engineers named it a State Historic Civil Engineering Landmark.

The three-acre site is split between DeSoto Parish, Louisiana (one acre), and Panola County, Texas (two acres); the granite marker itself belongs to the U.S. government. It stands near the junction of Texas Farm to Market Road 31 and Louisiana Highway 765, southeast of Deadwood, Texas, about 8 km from Logansport. The ground is low and swampy, near Toledo Bend Reservoir.

This is one of only two international boundary markers that sits entirely within present-day United States territory. Despite its location on major roads, it often goes unnoticed by passing travelers.