Shadab Khan and Haris Rauf put on an unbeaten 89 for the 10th wicket to take Pakistan to a one-wicket win over England in Lahore on Sunday.
It is the highest last-wicket partnership in a successful ODI chase.
The previous record of 64 had stood since the 1975 World Cup, when West Indies' Deryck Murray and Andy Roberts set it against Pakistan.
Chasing 242 in the tri-nation series, Pakistan were 154 for nine when Rauf walked out. Shadab did most of the scoring. Rauf's share of the stand was seven runs.
Shadab finished on 113 not out, his first ODI century. It was only the third century in ODI history by a batter coming in at No. 8 or lower.
He survived a close call on 97, with 21 still needed. Given out lbw the ball after hitting a six, he reviewed, and UltraEdge showed a faint spike as the ball passed the bat. The decision was overturned.
On 99, Tom Banton missed a chance to run out Rauf. Shadab, back on strike, reached his hundred with a four off Gus Atkinson, hit the next ball for four and finished the over with a six, leaving Pakistan needing three off 18 balls.
Rauf hit Henry Crocombe for four off the first ball of the next over to finish the match.
The win, Pakistan's third in a row, put the hosts into the final. England have lost all three of their matches, including the previous one, in which they scored 429.
Saad Baig's 32 was the second-highest score of Pakistan's innings.
Earlier, Ben Duckett made 105 off 111 balls as England were bowled out for 241. Harry Brook, who hit the fastest double century in ODI history in England's previous match, was out for one. Shaheen Afridi took four for 46.