The 52-year-old ex-midfielder, who appeared at Teesside Crown Court, denied the offence and insisted the kiss was not sexual.
The jury was told they could consider a lesser, alternative count of assault by beating if they cleared the footballer of sexual assault, but he was also cleared of this charge.
“You are now discharged and free to go,” Judge Peter Armstrong said.
The judge said Gascoigne can apply to have his defence costs paid.
Gascoigne wept in the dock as he was cleared of sexual assault – wiping his eyes and hugging his agent as he left court.
The court heard Gascoigne was loud and swearing as he drunkenly sat down next to the complainant, tapped her on the arm, grabbed her by the cheeks and planted a kiss on her lips.
Michelle Heeley QC, defending, told jurors the ex footballer kissed a woman in August 2018 who was not expecting it and did not like it but that did not mean he was a sex offender.
She said the kiss took place on a crowded train and lasted two or three seconds – adding it was not preceded by any “lecherous comment”, touching or groping.
She said while it might have been “misplaced”, it was not sexual.
After she was kissed, the woman, who cannot be named, was shocked and a fellow passenger challenged Gascoigne, saying: “What you have just done is sexual abuse.”
Police later tracked down Gascoigne to a hotel in Jesmond, Newcastle, where an officer spoke to him on the phone.
The footballer said: “I know what it’s about, I kissed a fat lass.”
When he gave evidence, Gascoigne said he was trying to reassure his alleged victim after he claimed to have overheard someone say: “You don’t want a photo with her, she’s fat and ugly.”
He spoke of his own battle with his weight, struggles with bulimia and bullying suffered by family members.
Gascoigne said he came and sat next to the woman, telling her: “Take no notice of what they say”, and “Listen, you’re not fat and ugly.”
He denied being drunk at the time, telling the jury he had undergone an operation in Australia to have pellets implanted in his stomach which would make him “spew up” if he drank spirits.
The defence showed the jury pictures of Gascoigne kissing and being kissed by other people, including former footballers Steve Bull, Ian Wright, Ally McCoist and Wayne Rooney, as well Diana, Princess of Wales.
The former Tottenham, Newcastle and Rangers player, who has struggled with alcoholism for many years, retired from football in 2004 and won 57 caps for England.
Additional reporting by Press Association