Esa Juwara threatened some of his victims with a knife and attacked others with a bicycle chain in a series of attacks on sex workers in the city between March 2019 and January 2020.
The 21-year-old was eventually caught after being spotted cycling around a Birmingham park and was picked out by three victims in ID parades and matched the descriptions given by the other two. DNA evidence from a sixth victim, who did not make a police complaint but gave evidence in court, also linked him to the offences.
Despite "overwhelming" evidence against him, Juwara, of Lighthorne Avenue, Ladywood, denied attacking all victims and claimed to be a virgin, the Crown Prosecution Service said. However he was found guilty of seven sexual assault charges by jurors this week.
Juwara began his campaign of sexual assaults in March 2019 after grabbing his first victim and threatening her with a knife, although she was able to escape after her friends heard her screams.
In July, Juwara attacked another sex worker on Ladywood Road, punching her and hitting her repeatedly with a bike chain after she refused his advances.
She managed to escape, but was accosted by Juwara three months later and was unable to fight him off as he punched her repeatedly and raped her.
Juwara went on to rape another sex worker on two separate occasions in November and December, again with the same level of violence.
Another was attacked twice in December, the first time saved by members of the public, but threatened with a knife and raped on the second occasion.
A fifth sex worker was attacked in Chamberlain Gardens by Juwara with his bike chain around her neck.
She passed out for a short time and awoke to find him raping her, before passers-by came to her rescue and Juwara made off.
He was caught in January of this year when plain-clothed police officers on patrol in Ladywood Park spotted a man on a bike matching the description of the rapist.
As the officers moved in to arrest Juwara, he threatened a female officer with his bike chain and made off despite CS spray being discharged before being apprehended nearby.
Juwara was found guilty of five counts of rape, one count of attempted rape and one count of sexual assault in court on Wednesday. He was also found guilty of two counts of committing an offence with intent to commit a sexual offence.
Detective Inspector Dave Bates, from the public protection unit at West Midlands Police, said: "These attacks were shockingly violent and becoming more frequent.
"The bravery of these women in coming forward is immense.
"They suffered such utterly degrading and violent crimes, yet found the courage to report them to us and give a detailed description of their attacker, helping us to catch him.
"They also had to relive their terror as they gave evidence in court.
"I commend the outreach programmes who supported them through their ordeals.
"They can be incredibly proud that they have prevented further attacks on more women as there is no doubt in my mind that Juwara would have continued his offending."
Nicola Heath of the CPS added: "Esa Juwara targeted his vulnerable victims. He subjected them to a terrifying sexual ordeal, and was prepared to inflict violence to get what he wanted. Despite the overwhelming evidence against him, he denied attacking all victims and claimed to be a virgin.
"The women were initially reluctant to complain due to the nature of their work, and they also feared no one would believe them.
"I want to take this opportunity to thank all of the victims for their bravery in coming forward and reporting the attacks and for giving evidence in such difficult circumstances. I hope this conviction sends a message that we take sexual offences seriously, irrespective of the victim's occupation or personal circumstances."