The 25-year-old Slovakian has the cycling world at his feet; he's one of the the highest paid professional cyclists and arguably the best-loved too. Known as much for his cheeky grin, honest race appraisals and the occasional TV interview photobomb, Sagan was crowned World Champion at Richmond, Virginia last weekend.
Ride Velo looks back at Sagan's 2015 - from crashing out of the Vuelta de Espana this summer, to being crowned Champion of the World, here is a tribute in pictures.
In January, Sagan and his older brother Juraj joined team Tinkoff-Saxo on a three-year contract. Peter Sagan's salary is thought to be in the region of $5 million a year, matching that of two-time Tour de France winner, Chris Froome.
After two second places, Sagan went on to win the White Jersey at the Tour of Qatar in the first race of the season, as the victor in the Young Rider category.
In May, the Tour of California saw Sagan repeatedly coming second, a pattern that was to stay and plague his season. He lost to Mark Cavendish in the first and second stages in nail-biting finishes, but took the race overall, with a tense three second lead.
A couple of wins in his hometown of Zilina, Slovakia, in June, and the Points Jersey in the Tour de Suisse, preceded the Tour de France.
The 2015 Tour de France saw a frustrating 5 second places throughout the 23 stages, and no single stage wins. However, this didn't dampen the famous Sagan sense of humour and he wowed TV viewers with his honest and funny interview style and cheeky behaviour, as seen in the video clip where he photobombed Vicento Nibali:
Despite being threatened with a pay cut back in May by team boss Oleg Tinkov for not performing strongly enough early in the season, Sagan went on to win the green Points Jersey in the Tour de France for the fourth consecutive year.
Sagan finally celebrated a stage win at La Vuelta de Espana in August, but the victory was short lived, after a motorbike crashed into him during stage 8. Sagan, understandably, flew into a rage and was fined 300 Swiss Francs by race organisers for his outburst. It was a very disappointing end to the race for him and his fans, and Tinkoff-Saxo demanded an apology for the incident.
September saw Sagan finally enjoying the fruits of his labours, in Virginia, USA. On Sunday 27th he won the World Race Championships in Richmond. He attacked on a short cobbled climb to win solo. A very well deserved victory for the young Slovak who started his cycling career as a cyclo-cross and mountain-biker.