Peter Sagan (Slovak pronunciation: [ˈpeter ˈsaɡan]; born 26 January 1990) is a Slovak former professional cyclist who competed in road bicycle racing and mountain bicycle racing. Sagan had a successful junior cyclo-cross and mountain bike racing career, winning the junior cross-country race at the 2008 UCI Mountain Bike & Trials World Championships, before moving to road racing. He ended his cycling career in 2024.

Sagan is considered a generational talent, having earned many prestigious victories out of a total of 121 professional wins. His most notable achievements were an unprecedented three consecutive men's road race World Championships from 2015-2017 inclusive, and his record seven points classifications in the Tour de France. He also won two of cycling's monuments, the Tour of Flanders (2016) and Paris–Roubaix (2018), and was awarded the prestigious Vélo d'Or in 2016, the season when he also topped the UCI World Ranking.

Born in Žilina, Peter Sagan is the youngest child among three brothers and a sister. He was brought up by his sister as his parents spent most of the day taking care of a small grocery shop they own in his hometown. His older brother Juraj Sagan was also a professional cyclist, and was also a member of the TotalEnergies team.

Sagan started to ride bikes at the age of nine when he joined Cyklistický spolok Žilina, a small local club in his home town. Throughout his junior years Sagan rode both mountain bikes and road bikes, and was well known for his unconventional style of riding in tennis shoes and T-shirts and drinking just pure water. Sagan drew a significant amount of attention when he appeared at the Slovak Cup with a bicycle borrowed from his sister. Sagan had mistakenly sold his own and had not received a spare from the Velosprint sponsor in time. He won the race despite riding a supermarket bike with poor brakes and limited gearing.

Sagan's first professional cycling opportunity came along when he was hired by the Dukla Trenčín–Merida team, a Slovak outfit in the Continental (third) division. In 2008, he won the Mountain Bike Junior World Championship in Val di Sole. That same year he also finished second in the junior race at the UCI Cyclo-cross World Championships in Treviso and Paris–Roubaix Juniors. Sagan was focused on continuing his career as a mountain bike rider, but his management company Optimus Agency approached several professional road cycling teams. They received four answers to bring young Sagan for testing. The first three-day test was performed in Quick-Step but Sagan failed to secure a contract. His frustration was so deep that he decided to quit road cycling, however pressed by his family he gave it a try with Liquigas–Doimo and succeeded.

In November 2009, Liquigas's Stefano Zanatta, Paolo Slongo and Enrico Zanardo offered Sagan, who spoke neither Italian or English, a ten-month contract valued at €1,000 per month. The agreement was later replaced by a two-year contract for 2010 and 2011 with an option to ride mountain bikes for Cannondale. Liquigas doctors and managers were stunned by results of Sagan's medical tests, saying that they had never seen a 19-year-old rider as physically strong and capable. During the training camp Sagan destroyed more mountain bikes than any other rider due to his ability to put a bike through its paces. This earned him the nickname "Terminator".

I do not want to be the second Eddy Merckx. I want to be the first Peter Sagan.

Liquigas selected Sagan for his first UCI ProTour road race, the Tour Down Under in January at the age of 19. He was involved in a crash during the second stage but kept riding with 17 stitches in his arm and left thigh. In the queen stage to Willunga he joined an attack over the last climb with Cadel Evans, Alejandro Valverde and Luis León Sánchez. The four fought to hold off the sprinters' group over the next 20 kilometres (12 miles), with Sánchez taking the win. Sagan won his two ProTour stages during Paris–Nice, a race he was not initially nominated for, but joined the team after his teammate Maciej Bodnar broke his collarbone. His first stage win was gained on the third stage, when Sagan joined a move initiated by Nicolas Roche on the final climb and out-sprinted Roche and Joaquim Rodríguez for the stage win in Aurillac. The result also gave Sagan the lead in the points classification, giving him the green jersey. Sagan's second win came from a solo attack on the fifth stage into Aix-en-Provence. Attacking three kilometres from the finish, on a steep climb, Sagan was able to hold off the peloton to claim the win.