American held his nerve in the big points and stood up well to his 20-year-old compatriot's blistering serve to reach his first Grand Slam semi.
Tommy Paul has become the first American man to reach the Australian Open semi-finals since Andy Roddick in 2009, after outclassing Ben Shelton 7-6(6) 6-3 5-7 6-4 in an all-American clash at Melbourne Park.
Paul held his nerve in the big points and stood up well to his 20-year-old opponent's blistering serve to reach his first Grand Slam semi on Wednesday.
He joins John Isner and Frances Tiafoe as the only active American men to have reached the last four of a major.
"Yesterday I was doing a lot of interviews where I was asked how it feels to be in the quarters, but the semis sound better," Paul said.
"I'm pumped to be here and exited to play in the next round. Doing well in a Grand Slam is everyone's dream."
Paul took a tight first set at Rod Laver Arena in a tiebreak after a fierce forehand prompted Shelton to crash a return into the net, and the 25-year-old went up 4-2 in the next set when Shelton's booming serve cracked.
Shelton, playing in the main draw of a Grand Slam for just the second time, began to spray errors around the court and world number 35 Paul took a 2-0 lead with his fourth ace of the contest.
Shelton got back into the match by taking the third set despite being down a break at 4-3 but Paul recovered from a dip in his level to go back on the offensive in the fourth.
Decisive early break
Cranking up the pressure on the Shelton serve, Paul got the decisive early break, though he could have gone up a double break at one point.
He missed that opportunity when his coach Brad Stine told him to expect a serve on the 'T', only for Shelton to see the signal on the big screen and fire wide for another ace.
The two players shared a chuckle about that later.
"I asked him (Stine), because I had trouble all day on breakpoints and big points and I didn't know where to lean and he screamed 'T' and I covered the 'T' but Shelton went wide," Paul said.
"I wasn't expecting that, but I'm really happy to get through that match. Ben's tough to play against and he's going to be in many matches like this."
Playing without fear, world number 89 Shelton fired 24 aces in the match, including some of the fastest serves in the tournament. But he was also hampered by 50 unforced errors.
Paul held firm from there to claim the victory and set up a last-four encounter with nine-times champion Novak Djokovic.