REO Speedwagon (originally stylized as R.E.O. Speedwagon), or simply REO, was an American rock band from Champaign, Illinois.

Formed in 1966, the band cultivated a following during the 1970s and achieved significant commercial success throughout the 1980s. Their best-selling album, Hi Infidelity (1980), contained four US Top 40 hits and sold more than 10 million copies.

REO Speedwagon sold more than 40 million records and charted 13 Top 40 hits, including the number ones "Keep On Loving You" and "Can't Fight This Feeling".

In the fall of 1966, Neal Doughty was a junior at the University of Illinois in Champaign, Illinois. On his first night of classes, he met fellow student Alan Gratzer. Doughty had learned some Beatles songs on his parents' piano, and Gratzer had been a drummer in local bands since high school. The two held an impromptu jam session in the basement of their Illinois Street Residence Hall dormitory.

Gratzer continued to perform with his band (which had a keyboard-playing lead singer), and Doughty began turning up at gigs. Doughty eventually began sitting in on a few songs. On the last day of the university's spring semester, guitarist Joe Matt called the band's leader and told him that he and the other members (Gratzer and bassist Mike Blair) had decided to start a new band with Doughty where everyone but Doughty would sing.

The new band made a list of songs to learn over the summer break. Doughty landed a summer job and bought his first organ. On his Farfisa organ, he learned The Doors' "Light My Fire". The members returned to school in the fall of 1967 and had their first rehearsal before classes started. They named the band REO Speedwagon, from the REO Speed Wagon, a 1915 truck designed by Ransom Eli Olds. Doughty had seen the name written on the blackboard when he walked into his History of Transportation class on the first day they had decided to look for a name. Rather than pronouncing REO as a single word as the motor company did ("REE-oh"), they chose to spell the word out, pronouncing each letter individually ("R-E-O"). An advertisement in the school newspaper produced their first job, a fraternity party that turned into a food fight. They continued to perform cover songs in campus bars, fraternity parties and university events.

In early 1968, Terry Luttrell became lead singer and Bob Crownover joined as the guitarist, replacing Matt after he graduated. When Mike Blair left the band in mid-1968, Gregg Philbin replaced Blair and Joe McCabe played sax until he moved on to Southern Illinois University. Marty Shepard then came aboard on trumpet, soon joined by a second trumpeter named Steve (last name unknown). Doughty joined them as a third horn player on some tunes. But Shepard left during the following year and horns were dropped from the group altogether by the summer of 1969.

Bob Crownover played guitar for the group until mid-1969, when Bill Fiorio replaced him. Fiorio then departed in late 1969, eventually assuming the name Duke Tumatoe, and went on to form the All Star Frogs. Steve Scorfina (who went on to found the band Pavlov's Dog) came aboard for over a year, composing with the band and performing live, before being replaced by Gary Richrath in late 1970.