Wavertree councillor Jake Morrison, who was elected in 2011 at the age of 18, said he will "retire" in May.
The now 22-year-old posted a statement on Facebook but does not give a reason for his decision.
However, he told the BBC he is disillusioned with the culture of politics, both locally and nationally.
Mr Morrison's decision comes a year after he was involved in a row with Labour MP Luciana Berger.
He was suspended by Labour after the Merseyside MP complained about his "complete lack of teamwork".
But he said the well-publicised disagreement was not the reason behind his decision to resign, and also abandon his ambition to become an MP.
"I don't want people to think that I don't like Luciana and that's why I'm not going to do this anymore," he said.
"It's difficult to explain without providing evidence, but I've suffered attacks on my character. Rather than focusing on my work, people have tried to discredit me.
"I've done enough to be confident that I've made a difference. But I don't think that the tactics and dirty games that are going on help anyone."
Mr Morrison added that he was "tired" of sitting in meetings in which councillors seemed preoccupied with "point scoring".
"Local and national politics is consumed with people simply trying to get one over on each other," he said.
Liverpool's youngest councillor has decided to stand down, blaming "tactics and dirty games" within local politics.