The Bandidos bikies have established a West Australian chapter after patching over the Rock Machine gang.
Acting detective inspector Jeff Christmass confirmed the Bandidos, which originated in Texas in 1966, had patched over the Rock Machine gang over the weekend.
"It's the same people involved, so there has not been any change in the actual numbers in the gang, just a different name," he said.
"WA police are monitoring the movements of this gang, as with all outlaw motorcycle gangs in this state, and will take the appropriate action as required."
The Bandidos website has a series of congratulatory posts with one stating: "Congratulations to the Bandido Nation for opening the west coast chapter in Perth."
Another post on the website reads: "A massive shout out to all the new west coast chapter. Love, loyalty and respect to all the boys. Out with the old and in with the Red and Gold."
The Bandidos emerged in Australia in 1983 following a split from the Comancheros.
The move into WA follows another bikie take over earlier this month with the notorious US-based Mongols patching over the Finks.
There were previously only three Mongols in WA and all are in prison.There are about 12 Finks members in WA and about half are in prison, while their club house has been frozen.