Sean Longstaff scored the winning spot-kick as Leeds edged through to the FA Cup's last 16 by beating Birmingham 4-2 on penalties after the tie finished 1-1 at the end of extra time.
Blues substitute Patrick Roberts struck an 89th-minute equaliser to cancel out Lukas Nmecha's second-half strike but Leeds held their nerve in the shootout.
Leeds quartet Joël Piroe, Dominic Calvert-Lewin, Brenden Aaronson and Longstaff all converted, while Tommy Doyle's effort for Birmingham was saved and Roberts fired his effort over the crossbar.
After Leeds had ridden a first-half storm, Nmecha's thumping finish soon after the restart looked set to send them through, but Roberts' late equaliser forced extra time.
Leeds, who won 3-1 at Derby in the previous round, will now bid to reach the quarter-finals for the first time since 2002-03.
Blues went close to taking an 11th-minute lead when Jay Stansfield's rising drive was brilliant finger-tipped on to the crossbar by Leeds goalkeeper Lucas Perri.
Blues revealed this week chairman Tom Wagner was recovering from a stroke and home fans unfurled a huge 'get well' banner before kick-off, while there was a minute's applause in the 13th minute in tribute to their American owner. Leeds sent their best wishes via a message posted on X on Sunday morning.
Birmingham swarmed all over Leeds in the opening 20 minutes. Jhon Solis and Kai Wagner saw shots held by Perri and skipper Christoph Klarer's header was blocked.
And Perri denied Birmingham what would have been a deserved lead just before the break with another full-length save to keep put Demarai Gray's low shot.
Leeds captain Ethan Ampadu replaced the ineffective Facundo Buonanotte at the interval and the visitors took the lead within four minutes of the restart.
Klarer lost out to Nmecha on the edge of the area and the striker crashed home a superb finish for his seventh goal of the season. It was Leeds' second effort on target.
Birmingham mounted a spirited response, forcing a series of corners as Stansfield fired wide and August Priske's effort was blocked.
But with Ampadu prominent, Leeds carried more of a threat in the second period, only for Roberts to conjure a late equaliser as his shot from outside the box flew in via a deflection off James Justin.
Calvert-Lewin, who had replaced Nmecha, saw his goalbound shot deflected over and in a frantic finish to the 90 minutes, Blues hit a post through Ibrahim Osman's low shot, with fellow substitute Kanya Fujimoto's follow-up effort blocked.
Osman spurned another chance at the far post in the first period of extra time, while Piroe, Calvert-Lewin and Ampadu all had chances for Leeds in the second as a thrilling cup-tie flowed from end to end before being decided on penalties.
Wolves withstand Grimsby effort
Wolves survived a mud bath in Grimsby to book their place in the FA Cup fifth round with a 1-0 win.
It was not pretty but Santiago Bueno's second-half strike was enough for the Premier League strugglers to get past their League Two opponents in less than hospitable surroundings.
The Mariners had beaten Manchester United in the League Cup earlier in the season and smelled more top-flight blood.
This would have been less of a scalp than their August win over United given Wolves' problems this season, and the treacherous conditions at Blundell Park were a definite leveller as the quagmire pitch made it impossible to play any quality football.
But Wolves survived a first-half scare to gain control and put their name in the hat for the fifth-round draw.
Late Fulham winner denies Stoke
Harrison Reed's opportunistic finish carried Fulham into the fifth round of the FA Cup as they came from behind to see off Championship strugglers Stoke 2-1 at the bet365 Stadium.
The Potters have not won a game since seeing off Coventry in the previous round, with three losses and three defeats, but started well against a Cottagers side showing 10 changes from their midweek defeat by Manchester City.
South Korean midfielder Bae Jun-ho capped a fine move by putting Mark Robins' team ahead after 19 minutes but they were overpowered as their Premier League opponents settled after the interval.
Brazilian winger Kevin got his reward for a livewire performance in the 55th minute, sending a first-time effort into the bottom corner after cutting in from the left, and a self-inflicted error cost the hosts dear with six minutes remaining.
Under siege for long periods, goalkeeper Tommy Simkin attempted a short pass to Tatsuki Seko, who was caught daydreaming by Fulham's captain-for-the-day Reed. He collected the ball as Seko tumbled to the turf, finished calmly and sealed the London club's place in the next stage.
Sunderland progress after controversial penalty
Sunderland reached the FA Cup fifth round for the first time since 2015 as Habib Diarra's contentious first-half penalty earned a 1-0 win away to Oxford.
The Championship side proved stubborn opponents on a pitch that had been lashed by rain earlier in the day, but the surface held out at the Kassam Stadium and so did Regis Le Bris' Premier League visitors, scraping through thanks to a decision that convinced few supporters in the home section.
Dennis Cirkin was the beneficiary, going over in the box under a challenge by Christ Makosso. With no VAR to advise, one look was all referee Thomas Kirk got and Diarra capitalised to help his team emerge from a tricky tie.