Highways bosses were forced shut both carriageways after heavy rainfall throughout the night and early hours of the morning.
Several minor roads in the area have also been affected by the flooding and Inspector James Scott of Surrey Police is urging motorists not to travel at present if at all possible.
Sussex Police Roads Policing Unit said the M23 was likely to remain closed “for several hours”.
Flooding has forced the closure of the M23 in both directions
Diversions are in place and motorists are being advised to allow extra time for their journeys.
Highways England said road users heading south should follow the “hollow diamond” diversion signs which will take them back onto the motorway at Junction 11.
Those travelling on the northbound carriageway should follow the “solid square” diversion signs off the motorway.
Motorists have also been warned there could be flooding on some parts of the diversion route.
Floodwaters cascade onto the M23 after a local river burst its banks
But some furious air passengers missed their flights from Gatwick – Britain’s second busiest airport – as a result of the delays and disruption caused by the motorway’s closure.
Nevin Jinha tweeted: “How on earth can a major motorway into London – the M23 be closed in both directions due to flooding?
“This is beyond unacceptable in this day and age. Constant roadworks causing chaos and still incompetence.
“Flight missed thank you very much.”
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Highways England tweeted a video and said: “This is the current situation at the scene of the flooding on the M23. As you can see it is quite a flow of water from the adjacent land on to the road.
“Our contractors are trying to deal with this as best as we can but the road is expected to remain closed for a while yet.”
Travel news service INRIX said: “M23 in both directions closed, queuing traffic due to flooding from Junction 10 (Crawley) to Junction 11 (Pease Pottage). Congestion to the junction for Handcross along the A23 northbound.
“Due to heavy flooding around J10A, police have closed the road.”
Transport bosses said the heavy rainfall was also causing major disruption on the railways in the southeast with the Southern, Thameslink and Gatwick Express network worst affected.
Services between London Victoria and Brighton have been suspended this morning after flooding in the Hayward’s Heath area.
Disruption is expected to continue into the afternoon but officials warned their could be more chaos to come.
Sussex Roads Police tweeted: “It’s a miserable morning for anybody hoping to travel north out of Sussex, both on the roads and the trains.
“Please be aware the M23 closure is likely to be prolonged due to even worse weather being forecast over the next few days.”