Valencia joined holders Barcelona, Real Madrid, Atletico Madrid and Sevilla, who got an automatic berth as last season's winners of Europe's second-tier Europa League.
On a night of pulsating action, Malmo, Dinamo Zagreb, Maccabi Tel Aviv and Shakhtar Donetsk also booked money-spinning group stage spots in Europe's premier club competition.
Former Manchester City forward Alvaro Negredo put Valencia in the driving seat with a deft fourth-minute chip but the Spaniards were forced to hang on after Andrea Raggi and Elderson revived Monaco's hopes in the principality.
“It was important to get an away goal and we managed that early in the match which helped calm things down,” Negredo told Spanish television. “In the second half they pressed forward and we were tiring but thankfully we held on.”
Swedish champions Malmo made the group stage for a second straight season after captain Markus Rosenberg and a Dedryck Boyata own goal gave them a bruising 2-0 win and 4-3 aggregate triumph over Celtic to overturn a 3-2 first-leg away deficit.
Former European Cup winners Celtic lost their lead after Rosenberg met a corner, the ball sliding in off his shoulder.
Malmo missed several chances before Boyata's desperate attempt to clear in a goalmouth scramble ended with the Celtic defender sliding the ball into his own net.
“We are at least as good as last year, particularly at home,” Rosenberg told Sweden's TV6 after Malmo kept a 10th straight clean sheet at home in European qualifying.
“A hard day's work, we did what we said we would do and the crowd were great as always.”
Dinamo qualified for the third time in the past five seasons, beating Skenderbeu 4-1 at home to complete a 6-2 overall victory against the Albanians.
Algeria striker El Arabi Hilal Soudani netted a fine brace, with Jeremy Taravel and Armin Hodzic also on the scoresheet for the Croatians.
A nervy 2-2 home draw with Rapid Vienna saw Shakhtar through 3-2 on aggregate after a 1-0 win in the first leg, while Maccabi edged out Basel on away goals, a 1-1 home draw being just enough following last week's 2-2 tie in Switzerland.
Shakhtar appeared to be cruising after Marlos doubled their aggregate lead but goals from Louis Schaub and Steffen Hofmann turned the tie on its head before Olexandr Gladkiy forced the final twist in a rip-roaring first half.
Maccabi progressed to the group stage for the second time after an Eran Zahavi goal cancelled out Luca Zuffi's opener.
The top clash among Wednesday's five games features Manchester United's visit to Bruges, where the three-time winners will defend a 3-1 first-leg advantage over the Belgians. – Reuters
Original source: Valencia beat Monaco in CL play-offs