Following his 2016 Liiga championship, Laine was named to the Finland roster at the 2016 IIHF World Championship, becoming the youngest Finnish player to ever play at the tournament. He debuted against Belarus, scoring two goals and one assist to become the youngest player in the tournament's history to score three points in a game. He followed this with a second consecutive two-goal, one-assist, three-point game against Germany, recording six points in two games to become the highest-scoring draft-age player in the tournament's history; the previous record was held by Jaromír Jágr, who at the same age scored three goals and two assists for five points in ten games at the 1990 Men's World Ice Hockey Championships in Switzerland. In Finland's final round robin game against Canada, Laine did not score but was considered by analyst Ray Ferraro among others to have had his best game of the tournament. Laine and Finland subsequently reached the gold medal game, a rematch against Canada, where they were defeated 2–0. Laine finished the tournament with 7 goals and 5 assists for 12 points in 10 games and led the tournament in goals scored. He achieved the second-highest point total by a U-19 player at a World Championship tournament, behind only Sidney Crosby's tournament total of 16 points at the 2006 IIHF World Championship. At the conclusion of the 2016 IIHF World Championship, Laine was named the tournament's Most Valuable Player, was named to the tournament All-Star team, and received the IIHF Directorate Award for the tournament's best forward.