Cologna collected the second Olympic cross-country gold medal of his career, having won the 15-kilometer freestyle event at the Vancouver Games four years ago.
After having ligament damage repaired, Cologna returned to competition in January and on a perfect day for skiing he demonstrated his fitness level had not suffered.
He was part of the lead pack throughout the race and then, as the medal contenders started their last trip up the slope that leads to the finish line, Cologna put on a burst.
Although the margin of victory was narrow, Cologna raised his arms in celebration two strides before he reached the line.
Cologna was timed in 1:08.15.4 for the 30 kilometers of racing. He defeated silver medalist Marcus Hellner of Sweden by fourth-tenths of a second. Martin Johnsrud Sundby of Norway was third, 1.4 seconds behind the winner.
The skiathlon requires the athletes to ski 15 kilometers using the classical technique and 15 more of freestyle. There is a pit stop between the two segments, during which the competitors change skis.
It took Cologna 30.9 seconds to complete his stop, the 15th quickest time among the 68 competitors.