Brandy Hurtt, 23, of Belle Center, Ohio, was reported missing by Logan County authorities on Wednesday.
Investigators searched an Ayersville, Ohio, residence, as well as the river.
The body was found at 1 a.m. yesterday, according to a statement issued by the Defiance County sheriff's department.
The Lucas County coroner's office is to do an autopsy.
Defiance County Sheriff Dave Westrick said Jeremy Lee Rucker, 23, of Defiance, would be charged with aggravated murder tomorrow or Tuesday.
Rucker is being held at the Corrections Center of Northwest Ohio on a parole violation out of Defiance County, authorities said.
Rucker and Hurtt had two children, ages 3 and 1.
The children lived with their mother but were visiting their father at the time she was reported missing, authorities said.
Rucker was on parole for theft from a bank, Sheriff Westrick said.
The investigation has included officials from several agencies in Defiance, Paulding, and Logan counties, plus state law enforcement agencies, the statement said.