They were discovered by a member of the public on the beach at Bracklesham Bay in Chichester, West Sussex, yesterday (Thursday, October 12).
The district council sent their foreshores team to investigate and a spokesman said: “They have removed them from the beach, but we are keeping a close eye on the situation in case more appear.
“The main bathing season is over, but we would urge surfers and people who still swim in the sea at this time of the year to be extra careful when in the water.
“This type of jellyfish can cause a reaction which in extremely rare cases can be fatal.”
Reports of Portuguese man-of-war near the Sussex coastline are very rare, but usually occur earlier in the year, the spokesman said.
There have been recent reports in places such as Cornwall and Wales, said the spokesman.
Anyone who spots a Portuguese man-of-war is advised to leave the water and report the sighting by contacting the council on 01243 785166.