The Los Angeles Lakers honored the late Kobe Bryant with a tribute before the first game following his death ... with emotional performances by Usher and cellist Ben Hong ... and a powerful speech by LeBron James.

The Lakers superstar took center court to address the fans in attendance ... and spoke straight from the heart, calling Kobe his brother and the event a celebration of his career.

"I got something written down, they asked me to kinda stay on course, or whatever the case may be," LeBron said. "But Laker Nation, I would be selling y'all short if I read off this sh*t, so I'ma go straight from the heart."

"I look at this as a celebration tonight. This is a celebration of the 20 years of the blood, the sweat, the tears, the broken-down body, the getting up, the sitting down, the everything, the countless hours, the determination to be as great as you could be."

"I wanna continue along with my teammates to continue his legacy. Not only for this year, but as long as we can play the game of basketball that we love, because that's what Kobe Bryant would want."

James finished his speech with the message -- "So in the words of Kobe Bryant, 'Mamba Out' ... but in the words of us, 'Not forgotten.' Live on, brother."

Prior to LBJ's words, Usher performed a strong rendition of "Amazing Grace" while the video board showed a montage of the tributes that have popped up throughout the world, and Hong played while Bryant's on-and-off the court accomplishments flashed on the screen for all the fans to enjoy.

The Lakers then posted the names of all 9 people lost in the tragic helicopter accident and honored them with a 24.2 second moment of silence while the board showed the 2 courtside seats draped with Kobe and Gigi's jerseys.

Boyz II Men performed the National Anthem ... with all 3 members wearing the Kobe shirts handed out to every fan in attendance. Several players -- including LeBron -- broke down in tears during the performance.

The Lakers players honored Kobe by wearing Kobe's #8 and #24 jerseys during warmups ... and each player was announced as Kobe Bryant for the starting lineups.

LeBron wore Kobe's signature shoes, which might be the first time he's worn anything other than his own sneakers in an NBA game.

The Lakers and Portland Trail Blazers followed other teams' lead by opening the game with 24-second shot clock and 8-second violations.

Kobe's #8 and #24 were displayed on the court ... as well as a "KB" badge on the players' jerseys.

The fans were shouting Kobe's name outside Staples before entering the arena ... and we have video of the emotional scene.

Carmelo Anthony -- who was very close with Kobe -- did not make the trip because he's still mourning Kobe's death.

James revealed his permanent tribute to Kobe before the game, a tattoo that reads "Mamba 4 Life."

The memorials outside Staples continued to pour through LA Live on Friday ... and TMZ Sports was able to capture some of them.