Late strikes by Eden Hazard and Nemanja Matic fired Chelsea into the FA Cup final over Tottenham in a thrilling 4-2 win at Wembley.
Second-half substitute Hazard smashed home from just inside the box on 75 minutes before Matic's stunning hit sealed victory over their Premier League title rivals.
Willian, who replaced Hazard in a number of surprising changes by Antonio Conte, twice put the Blues ahead - the first a free-kick (5) and the second a well-taken penalty (43) that ensured they led at the interval.
Spurs dominated possession and were dragged back first by Harry Kane's skilful header (18) and then by Dele Alli's close-range effort (52) before Conte's men cruised clear to book a showdown with Arsenal or Manchester City.
Both teams paid tribute to Ugo Ehiogu before kick off with a minute's applause following the tragic passing of the Spurs U23 head coach on Friday.
Conte and Mauricio Pochettino made eight changes between them as Diego Costa dropped to the bench for Chelsea and Heung-min Son started at left wing-back for Spurs.
The Chelsea boss set his team up to counter and they did to perfection to open the scoring, generating a swift move started by Nathan Ake, who replaced the sick Gary Cahill.
Pedro burst through and looked destined to score but was hauled down by Toby Alderweireld in a glorious shooting position. Willian made no mistake with the set-piece, whipping the ball over the wall and past Lloris via a slight deflection.
Spurs immediately hit back as Christian Eriksen picked out Kane and the forward flicked his header beyond Thibaut Courtois.
Tottenham kept up the pressure and went close with a header from Eric Dier and a curling shot from Eriksen, but they were caught out at the back once again as Son - forced to play an unfamiliar role in place of Ben Davies - fouled Victor Moses in the box.
Willian stepped up and sent Lloris the wrong way to bag his second in a fervent display by the Brazilian.
Pochettino's side dominated the second half as they did the first, and equalised again when Alli met Eriksen's brilliant cross.
Alli had a penalty shout turned down but Tottenham's Wembley heartache at the hands of Chelsea - who beat them in their previous FA Cup semi-final appearance in 2012 and the League Cup final in 2015 - was about to continue.
Hazard and Costa were introduced and were both nuisances as Chelsea won a corner, which was cleared straight to Hazard, who thrashed into the far corner from 18 yards.
And, as Spurs committed bodies forward, Matic was afforded too much space on the edge of the box, allowing him to blast in Chelsea's fourth via the crossbar.
The Blues will contest their 12th FA Cup final against either Arsenal or Manchester City, who play on Sunday.
Player ratings
Chelsea (3-4-3): Courtois (6); Azpilicueta (6), David Luiz (7), Ake (7); Moses (7), Kante (7), Matic (7), Alonso (7); Willian (8), Batshuayi (6), Pedro (6)
Subs used: Fabregas (6), Hazard (8), Costa (7)
Tottenham (3-4-3): Lloris (6); Dier (7), Alderweireld (6), Vertonghen (7); Trippier (7), Wanyama (7), Dembele (7), Son (6); Eriksen (7), Kane (7), Alli (8)
Subs used: Walker (6), N'Koudou (6)
Man of the Match: Willian