Three goals in nine second-half minutes helped Chelsea beat Basel 3-1 and seal a 5-2 aggregate win that secures their place in the Europa League final.
Rafa Benitez's men found themselves behind at the break thanks to Mohamed Salah's strike in first half stoppage time.
However, quick-fire goals from Fernando Torres, Victor Moses and David Luiz at the start of the second half put Chelsea in command and into their second successive European final.
Frank Lampard captained the side as he chased the goal that would equal Bobby Tambling's all time record and he had the first chance of the game on nine minutes, his scuffed volley rebounding off the post with Yann Sommer beaten.
Torres had an effort from distance smartly saved by the Basel 'keeper nine minutes later before Ramires shot straight at Sommer midway through the half following good work by Moses and Eden Hazard.
Basel appeared to be galvanized by Chelsea's profligacy and stunned Stamford Bridge by taking the lead with virtually the last kick of the half.
Valentin Stocker's neat through ball found Salah, who had seen an earlier effort saved, but made no mistake this time with a cool first-time finish beyond Petr Cech.
That meant for a nervy 15 minutes for the home crowd, who knew another goal for the visitors would send them through.
Whatever boss Benitez said at half-time worked wonders though as Chelsea stormed out of the blocks in the second half.
After 50 minutes Lampard's shot from the edge of the box was fumbled by Sommer, allowing Torres to slam home the rebound.
Just two minutes later Moses was alert to pounce onto Torres' blocked shot and convert into the corner from close range.
The goal of the night was reserved for Luiz seven minutes later, the Brazilian curling a wonderful fizzing effort beyond a motionless Sommer and into the top corner.
The three-goal blast knocked the stuffing out of Basel, allowing the Premier League side to see the game out and secure a meeting with Benfica at the Amsterdam Arena on 15th May.
| Chelsea | Team Statistics | Basel |
| 3 | Goals | 1 |
| 0 | 1st Half Goals | 1 |
| 12 | Shots on Target | 5 |
| 7 | Shots off Target | 11 |
| 3 | Blocked Shots | 6 |
| 7 | Corners | 4 |
| 8 | Fouls | 13 |
| 2 | Offsides | 2 |
| 1 | Yellow Cards | 3 |
| 0 | Red Cards | 0 |
| 81.6 | Passing Success | 81.8 |
| 16 | Tackles | 36 |
| 68.8 | Tackles Success | 77.8 |
| 44.6 | Possession | 55.4 |
| 52.6 | Territorial Advantage | 47.4 |
| 380 | Total Passes | 490 |
| 22 | Total Crosses | 14 |
| 154 | Lost Balls | 146 |
| 61 | Recoveries | 54 |
| 47.3 | 1st Half Poss. | 52.7 |
| 39.5 | 2nd Half Poss. | 60.5 |
The Cobblers were good value for their narrow win heading into Sunday's second leg at Whaddon Road, but the Robins will feel more than capable of turning the tie around and returning to Wembley 12 months after their final defeat to Crewe.
O'Donovan's well-taken finish, his sixth goal of the season, came midway through the first half from Chris Hackett's right-wing cross.
Burly striker Adebayo Akinfenwa was denied a precious second goal for Northampton when he saw his close-range header kept out by a tremendous one-handed save by Scott Brown.
Paul Benson spurned two gilt-edged chances for Cheltenham while Jermaine McGlashan could feel hard done by not to have been awarded a second-half penalty when he was brought down, but the visitors failed to really trouble Lee Nicholls at Sixfields.
It was Northampton's first win in seven attempts over the Robins, who completed a league double this season, but the semi-final is far from over as both teams chase a return to England's third tier for the first time since 2009.
Cobblers boss Aidy Boothroyd was keen to stress pre-match that form counts for little heading into the play-offs, with his charges having ended a five-match winless streak on the final day of the regular season.
But even he could not deny that both sides have enjoyed starkly contrasting home and away form this term.
The Cobblers had won 11 of their previous 12 home games going into this one while the Robins are unbeaten in 20 at Whaddon Road, yet they had only managed 10 wins on the road between them.
With that in mind the onus was very much on Northampton to make the running tonight and it was they who settled first, with recalled pair Akinfenwa, twice, and Hackett off target.
Akinfenwa headed Ben Harding's 16th-minute corner goalwards but appeared to see his effort deflect off the arm of a Cheltenham shirt from close range.
And it was the hosts who took the lead in the 26th minute courtesy of a fine finish from O'Donovan, connecting with Hackett's cross from 12 yards.
Benson dragged wide a great chance to draw Cheltenham level immediately, and it was his header which forced Cobblers goalkeeper Nicholls into his first save in the 41st minute.
McGlashan made Nicholls tip over three minutes into the second half before Ishmel Demontagnac tested Brown at the other end while under pressure from Sido Jombati.
Benson then wasted another clear chance for Cheltenham just before the hour mark when he headed wide Marlon Pack's cross at the far post.
Cheltenham goalkeeper Brown produced a superb save to keep out Akinfenwa's 68th-minute header.
McGlashan could consider himself unlucky not to earn a penalty in the 70th minute having been clattered by Luke Guttridge.
It was Northampton who made all the pressing in the closing stages as they went in search of a crucial second but it failed to arrive and, despite a celebratory pitch invasion from the home support, the tie remains wide open ahead of the second leg.
The Bantams made it to the home of football earlier this season when they famously reached the Capital One Cup final, but they were undone by a superb first-half showing from the Brewers, who go into Sunday's second leg firm favourites.
Calvin Zola was the chief destroyer as he helped himself to a six-minute double with a bullet header and then a delightful curled effort.
In a frantic opening period, the Bantams hit back through Nahki Wells' penalty before the visitors again went two in front, courtesy of Robbie Weir's drilled finish.
Phil Parkinson's men did at least salvage some hope when Garry Thompson scored from distance with a fine effort to reduce their arrears - but Burton return to home soil, where they won 17 of 23 games in the regular campaign, with their lead intact and confident of gracing the Wembley turf themselves.
Having lost only one of their last nine games of the regular campaign, Bradford were the form team going into the play-offs and they were backed by a boisterous home crowd hungry for another night like those against Arsenal and Aston Villa in the League Cup.
But after a cagey opening, Burton had clearly not read the script and took the lead in the 22nd minute with a goal created by the fine wing play of Jacques Maghoma.
He picked up the ball on the left, found a yard of space and delivered a delightful ball that Zola headed in at the far post with power.
It got even better six minutes later as Zola, this time his own architect, stunned Valley Parade.
The striker picked up the ball at the far post and cut inside to curl a superb effort past Jon McLaughlin, although replays suggested he was offside.
The Brewers, who were beaten here in the league 11 days ago and in the early part of City's League Cup run, were in dreamland and it could have been even better when a slick passing move cut Bradford wide open and John McGrath was denied by the body of McLaughlin.
But 10 minutes later the Bantams hauled themselves back into the contest from the penalty spot.
They broke down the left, the ball fell to Thompson who thrashed a shot into the body of Damien McCrory, with referee James Adcock judging the defender to have handled.
Wells stepped up and coolly sent Stuart Tomlinson the wrong way from 12 yards.
However, the home resurgence was short-lived as the visitors restored their two-goal cushion two minutes before the break when Weir drilled home from 14 yards after Alex MacDonald's cross to put Burton in the box seat and leave Bradford exiting the pitch at half-time to boos.
Despite the hosts' need for to rescue something out of the second period it was Burton that continued to look more dangerous with Zola heading wide and then McGrath forcing McLaughlin into a sprawling save.
After the visitors took Zola off, Bradford seized the initiative and laid siege on Burton's goal - and Thompson got a potentially vital effort with 20 minutes remaining, the former Scunthorpe man curling a sumptuous 25-yard shot home.
The Brewers had barely been out of their half for 20 minutes, but MacDonald had an instant chance to hit back, although his effort from 14 yards clipped the top of the bar.
Burton survived a late onslaught to prevail and take a precious lead back to Staffordshire.
