Rangers are 1-0 down in the tie, following a unstoppable strike from wing back Angelino at the Red Bull Arena in the first leg.
Giovanni van Bronckhorst’s men defended well during the match, limiting the German side to a few chances, and almost came away with a 0-0 draw - a big advantage going into the second leg at home.
But, on the 85th minute, Angelino responded first to a headed clearance from a corner, catching the ball first time on the edge of the D and striking in into the bottom left corner, out of Allan McGregor’s reach.
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It gives RB Leipzig a slender advantage heading to Ibrox, although the hosts will be confident of turning the tie around, having come back against Braga in the quarter finals after suffering the same result in the first leg and then winning the tie in Govan.
The Gers suffered disappointment at the weekend when they could only get one point from the final Old Firm clash of the season - Fashion Sakala struck the post late on, missing the chance to close the gap at the top of the Scottish Premiership to one point.
Celtic are now six points clear with three games remaining, and look set to win the title and earn an automatic spot in the Champions League group stages next season.
Now Rangers’ full attention will be on their Europa League games, with the aim of reaching their first European final since 2008.
Is Rangers v RB Leipzig on TV?
The second-leg fixture is being shown on BT Sport 2, with the coverage starting at 7pm.
The match itself kicks off at 8pm, with coverage continuing with post match analysis until 10.30pm.
At the same time, BT Sport 1 is showing the second leg of the other semi final - Eintracht Frankfurt v West Ham United - with the winner facing either Rangers or RB Leipzig in the final.
Latest Rangers v RB Leipzig betting odds
The German side are favourites, according to the bookies, at 11/10 to win the match. Rangers are further out at 45/17.
A draw is at 17/6.
Leipzig are also massive favourites to get through to the final (2/9 compared to 17/4 for Rangers) while French goalscorer Christopher Nkunku is 26/5 to be the first scorer.