A police officer made the frightening discovery on the M62 westbound on Wednesday, between junction 24 and junction 23 near Huddersfield.
PC Martin Willis, known as Motorway Martin on social media, shared a video of a cyclist riding along the hard shoulder - straight past a sign warning drivers of his presence.
Traffic was limited to 60mph while PC Willis escorted the man to safety.
PC Willis tweeted: "There are many types of conveyances that are prohibited from using the motorway.
"Bicycles are one of them!"
The video was met with a furious reaction on Twitter, with one user calling the incident "madness".
Another said: "That is *nuts*. I do think there should be cycle lanes alongside (and slightly higher) than motorways though. Would be handy for local commuters".