Ame Van Iden, a publicist for the American actor, confirmed the 40-year-old died in a smash north of Los Angeles on Saturday afternoon.
A statement on Walker’s Facebook page said he was a passenger in a friend’s car and had been in the area to attend a charity event for his organisation Reach Out Worldwide.
“We … are stunned and saddened beyond belief by this news,” it said.
The red Porsche reportedly crashed into a lamp post and burst into flames, killing them both.
Photos from the scene showed a pile of twisted metal and broken windows.
The Los Angeles County Sheriff’s Department said officers found the car engulfed in flames when they responded to a report of a collision in the Valencia area.
The two people, Mr Walker and a friend said to be Rodger Rodas, found in the car were pronounced dead at the scene.
Hollywood reporter Gayl Murphy said the actor had been travelling back from the fundraiser when the crash happened.
She told Sky News: “This is such a sad story. He was such a nice guy. Bystanders thought that the Porsche that they were driving in had gone out of control in a fiery crash.”
Walker was working on the seventh Fast And Furious movie at the time of his death.
“All of us at Universal are heartbroken,” Universal Pictures said in a statement.
“Paul was truly one of the most beloved and respected members of our studio family for 14 years, and this loss is devastating to us, to everyone involved with the Fast And Furious films and to countless fans.”
Co-star Vin Diesel posted a photo of himself with Walker on Instagram and wrote: “Brother I will miss you very much. I am absolutely speechless. Heaven has gained a new Angel. Rest in peace.”
“Your humble spirit was felt from the start,” said co-star Ludacris on Twitter.
“Wherever you blessed your presence you always left a mark, we were like brothers.”
Walker also starred in the suspense drama, Hours, which was set for release this month.