Definitely. TMNT started as a comic. Its success in the comic world led to its adaptation into various forms of media. The comic version was the original source that sparked the franchise.
The origin of the Teenage Mutant Ninja Turtles is really interesting. There was this mutagen that was created. Four turtles happened to come into contact with it in the sewers. Along with them, a rat was also affected by the mutagen. This rat, Splinter, had been observing the ways of ninjutsu from his owner before the mutation. After they all mutated, Splinter taught the turtles ninjutsu. They grew up in the sewers and became the Teenage Mutant Ninja Turtles we know. Their existence was soon discovered by April O'Neil, and they got involved in various battles against the evil forces in New York, especially the Foot Clan led by the menacing Shredder.
The availability of Teenage Mutant Ninja Turtles comics online varies. Sometimes you can find them on official comic publishers' websites, while other times they might be on third-party platforms. Just need to do a bit of searching.