Women's Champions League: Lyon Feminines 2-1 Chelsea Women
Erin Cuthbert's well-taken away goal gave Chelsea hope for the second leg as they lost to holders Lyon in their Women's Champions League semi-final.
Lyon, who have won the title five times since 2011, led 2-0 after Magdalena Eriksson's own goal and Amandine Henry's faint flick from a corner.
England's Fran Kirby then had a penalty saved on the stroke of half-time.
But a fine half-volley from Scotland's Cuthbert saw a spirited Chelsea halve the deficit in the second half.
Emma Hayes' side are bidding to reach the final for the first time, whereas the French club are targeting their eighth in nine years, having dominated the competition in this decade.
But the Londoners had chances to score more than just one away goal, despite having to withstand several periods of pressure from the hosts.
The first-leg result means Chelsea will progress to the final in Budapest on 18 May if they win next Sunday's second leg at Kingsmeadow 1-0 or by two goals or more if Lyon score.
Things looked bleak for the Blues after Eriksson - who was attempting to block the lively Delphine Cascarino's shot - inadvertently diverted the ball past Ann-Katrin Berger at her near post.
It was an unfortunate second own goal in as many games for an otherwise resolute Eriksson, who also turned the ball past Berger late on in last Sunday's Women's FA Cup semi-final loss to Manchester City.
Then Chelsea went to sleep from Dzsenifer Marozsan's left-wing corner, as the Germany midfielder curled the ball almost directly in, but it seemed to take a touch off Henry at the near post on its way through.
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The visitors, though, were creating promising openings of their own and had the chance to score in first-half stoppage time after Ramona Bachmann went down under Eugenie Le Sommer's challenge.
Kirby's spot-kick was straight at Sarah Bouhaddi, and the French keeper did well again moments after half-time to deny Chelsea's Maren Mjelde from close range.
Lyon - whose side included England right-back Lucy Bronze and Wales midfielder Jess Fishlock - continued to see more of the ball, before Cuthbert's superb strike from substitute Beth England's knock-down.
The away goal gave the Blues a platform to build on, as they bid to add to this seasons' aggregate wins over Paris St-Germain, Italian side Fiorentina and SFK 2000 Sarajevo of Bosnia and Herzegovina.
The match was watched by a crowd of 22,911 in Lyon, which was the largest attendance the competition has seen in a round before the final.
In Sunday's other semi-final second leg, Spanish giants Barcelona won 1-0 at Bayern Munich to take control of the tie and give themselves a great chance of reaching their first final.