The 1990 Monaco Grand Prix was a Formula One motor race held on 27 May 1990 at Monaco. It was the fourth race of the 1990 Formula One World Championship and the 48th Monaco Grand Prix. The race was held over 78 laps of the circuit for a race distance of .
The race was won by Brazilian driver Ayrton Senna, driving a McLaren-Honda. Senna started from pole position, led every lap and set the fastest race lap, en route to his second consecutive Monaco win and third in all. French driver Jean Alesi finished second in a Tyrrell-Ford, with Senna's Austrian teammate Gerhard Berger third.
Qualifying
Pre-qualifying report
The four successful pre-qualifiers in the one-hour Thursday morning session were the same four drivers as at the previous race at Imola, in the same order. The Larrousse-Lola cars finished first and second for the third time in a row, with Éric Bernard again outpacing his teammate Aguri Suzuki. The Osella of Olivier Grouillard was third fastest, followed by Roberto Moreno in the EuroBrun.
The AGS drivers were frozen out in fifth and sixth, with Gabriele Tarquini considerably faster than Yannick Dalmas on this occasion. Seventh was Claudio Langes in the second EuroBrun, six seconds off Bernard's pace. The other two runners were far behind; Bertrand Gachot was over twelve seconds adrift in the Coloni after another engine failure, with the team now in some disarray, but still nearly two seconds faster than the Life, driven again by Bruno Giacomelli. This time, however, the Italian managed to complete a stint of seven laps and return to the pits without breaking down. Well off the pace, Giacomelli went back out on to the circuit and completed another lap before the W12 engine failed.
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Championship standings after the race
;Drivers' Championship standings
{| class="wikitable" style="font-size: 95%;"
|-
!Pos
!Driver
!Points
|-
| 1
| Ayrton Senna
| align="right"| 22
|-
| 2
| Gerhard Berger
| align="right"| 16
|-
| 3
| Jean Alesi
| align="right"| 13
|-
| 4
| Alain Prost
| align="right"| 12
|-
| 5
| Riccardo Patrese
| align="right"| 9
|-
!colspan=4|Source:
|}
;Constructors' Championship standings
{|class="wikitable" style="font-size: 95%;"
|-
! Pos
! Constructor
! Points
|-
| 1
| McLaren-Honda
| align="right"|38
|-
| 2
| Williams-Renault
| align="right"|18
|-
| 3
| Ferrari
| align="right"|15
|-
| 4
| Tyrrell-Ford
| align="right"|14
|-
| 5
| Benetton-Ford
| align="right"|10
|-
!colspan=4|Source: