The Auglaize River is a 113-mile-long (182 km) tributary of the Maumee River in northwestern Ohio in the United States. It drains a primarily rural farming area in the watershed of Lake Erie. The name of the river either comes from a French term for "frozen water."

It rises in southeastern Allen County, approximately 10 miles (16 km) southeast of Lima and 12 miles (19 km) north of Indian Lake. It flows southwest to Wapakoneta, then generally north in a zigzag course, past Delphos, Fort Jennings and Oakwood. It joins the Maumee from the south at Defiance, approximately 2 miles (3 km) east of the mouth of the Tiffin River.

It receives the Ottawa River from the southeast in western Putnam County, northwest of Lima. It also receives the Blanchard River in western Putnam County. It receives the Little Auglaize River from the south in eastern Paulding County. It receives Flatrock Creek from the west in northeastern Paulding County.

During the days of the Ohio Country in the 18th century, the area around the river was inhabited by the Ottawa. Fort Amanda, constructed along the river southwest of Lima in 1812, was an important American outpost during the War of 1812. Fort Defiance was constructed in 1794 near the confluence of the Auglaize and the Maumee by General Mad Anthony Wayne.

en.wikipedia.org/wiki/Auglaize_River