The United States' Brandon McNulty, left, edged out Ben Healy of Ireland, centre, and Italy's Marco Frigo, right, on the 15th stage of the Giro d'italia ©Getty Images

American rider Brandon McNulty triumphed in a three-way sprint from the breakaway to earn a maiden Grand Tour victory on the 15th stage of the Giro d'Italia in Bergamo.

After several days of tough weather on the Giro including heavy rain which led to Thursday's (May 19) 13th stage being significantly shortened, conditions were milder and more favourable for the most part of the 195 kilometres mountain route beginning in Seregno and featuring almost 4,000 metres of climbing.

The peloton again opted to conserve energy, meaning there was no change at the top of the general classification and the stage favoured the breakaway.

Intermarché-Circus-Wanty rider Niccolò Bonifazio, competing on his home Grand Tour, made the first major move from the initial breakaway of 17 with around 50km remaining.

However, he was reeled in by his compatriot Marco Frigo racing for International Cycling Union ProTeam Israel-Premier Tech, EF Education-EasyPost's Irish rider Ben Healy and McNulty of UAE Team Emirates on the Roncola Alta climb, which peaked at a 17 per cent gradient.

Colombian 13th stage winner Einer Rubio of Movistar Team initially worked with Healy to bridge the gap to the leading group, but was dropped.

Frigo required a big effort on the Roncola Alta descent to bridge a gap of nearly 40 seconds and complete the front three.

Having lost ground on the climb and cobbles en route to Bergamo's old town, Frigo appeared to have timed his sprint well for a sensational comeback victory on the final strait.

However, McNulty and Healy hit back, and it was the American who prevailed in 5 hours 13min 39sec to become the first rider from his country to triumph on this year's Giro.

"I’m stoked," McNulty said.

"This was my goal coming here.

"I wanted a stage win but I got sick in the time trial.

"I wanted to finish solo but luckily I managed to win even in a sprint.

"I knew the third guy was coming across."

Healy finished second and Frigo third.

France's Bruno Armirail had his general classification lead trimmed, but remains in pink going into tomorrow's rest day ©Getty Images
France's Bruno Armirail had his general classification lead trimmed, but remains in pink going into tomorrow's rest day ©Getty Images

The group featuring main contenders Geraint Thomas of Ineos Grenadiers, Team Jumbo-Visma's Primož Roglič and McNulty's team-mate João Almeida finished 6min 53sec behind the front three.

Groupama-FDJ's Bruno Armirail became a surprise general classification leader yesterday, making him the first French rider to hold the Giro's pink jersey in the 21st century.

He had his lead trimmed from 1:41 to 1:08 by British rider Thomas, but will go into tomorrow's second and final rest day with an overall lead.

Slovenian race favourite Roglič and Almeida from Portugal, who continues to lead the young rider classification, were unable to gain any seconds on Thomas.

Roglič is two seconds further back than him, and Almeida 22 seconds.

Italian riders continue to lead the points and mountains classifications on their home Grand Tour in Team Bahrain Victorious' Jonathan Milan and Eolo-Kometa's Davide Bais respectively.

Six stages remain after tomorrow's rest day, beginning with the 203km mountain stage from Sabbio Chiese to Monte Bondone, featuring more than 5,000m of ascent and a difficult summit finish.