Corey Gamble says he heard Blac Chyna threaten to kill Rob Kardashian multiple times during the night of their blowout fight … once over the phone and again in person.

Corey was called to the stand Tuesday for the first time in Chyna’s trial, giving his account of the fight the Kardashians say was very violent.

CG, who told the jury Kris Jenner is his partner in life, testified he was awoken that night from an incoming call from Rob to Kris … and when Kris put the call on speaker, he heard Chyna screaming in the background over Rob.

Corey says he heard Chyna say to Rob … “F*** you, I’m a kill you fat mother f*****.”

Seeing it as a volatile situation, Corey says he knew he needed to help Rob, so he jumped out of bed, got dressed in a hurry and rushed over to Kylie Jenner‘s house only a few blocks away, where Rob and Chyna were staying.

Corey says he parked behind Rob’s car and headed to the front door, which was unlocked. While he went alone, Corey says Kris wanted to go too, but he told her to stay put because he feared the situation could be dangerous.

At the front door, Corey says he heard Chyna shouting at Rob in anger, telling him she hated him and threatening that she “would kill him.”

Once inside, Corey says he saw Chyna about 7 feet away from Rob, and she was holding a large rod of some sort in her hand, which she dropped when she saw Corey.

Chyna then ran towards Rob and picked up a long phone charging cord, Corey testified, whipping Rob and hitting him on his shoulder.

Corey says he jumped between them to break them apart and was hit in the process. He told the jury he told Rob to “get the hell outta here” because he thought the situation was dangerous, also testifying Chyna reeked of booze.

CG says Chyna took off after Rob as he tried to leave, telling the jury she was furious and wanted to keep attacking, but Corey says he stopped her from chasing after Rob and even tried to hide her keys.

Realizing he had blocked in Rob’s car with his own, Corey says he went outside to move his whip … but when he did, Chyna jumped back on Rob and continued hitting him, striking blows to Rob’s head.

Corey says Chyna then took a nearby patio chair and threw it at Rob’s car, hitting the front, and then tried to grab a small table and throw it as well … but Corey says he stopped Chyna from doing so.