The 19-year-old's body was found near Ponte Marconi on Monday morning, police confirmed in a statement on Monday night.
An investigation, led by prosecutor Marcello Monteleone, has been opened.
Solomon had arrived in Rome on Thursday to undertake a five-week course at John Cabot University.
The student from the University of Wisconsin-Madison was reported missing the next morning by his flatmate, who “was worried when he did not see Beau at orientation that morning”, John Cabot University said in a statement on its website on Sunday.
The friend had reportedly lost contact with Solomon at around 1am while together at a bar in Rome's popular Trastevere area.
His parents flew to the capital on Sunday.
The university said in a statement on Monday that it is "deeply saddened to announce that the body of Beau Solomon, the missing American visiting student, has been found in the Tiber River.
"We express our most heartfelt condolences to the Solomon family and to all those who loved Beau."
American student missing in Rome - Beau Solomon, 19 https://t.co/cc9e774Eh8— Ansa English News (@ansa_english) July 4, 2016
Police and family reportedly said his credit cards had been used since his disappearance. His phone was also stolen, according to reports, leading police to suspect his death could have been the result of a robbery, Ansa said. Some USD 1,500 (€1,346) had been charged to his credit card, La Repubblica reported.