NBA legend Bill Walton -- arguably the biggest Grateful Dead fan on the planet -- received a huge tribute at the Dead & Company Sphere show Thursday night ... three days after he tragically passed away.
The band -- which consists of John Mayer and Bob Weir, plus other former Grateful Dead members -- projected images of Walton behind them throughout their hourslong concert at the must-see attraction in Las Vegas.
Some of the pics displayed on the building's massive screens included Walton with Weir and Mickey Hart. They also featured the former Celtics center's No. 32 jersey number, rose petals ... and a whole bunch of tie-dye colors.
A rep for the band tells TMZ Sports ... the projections first began during the artists' rendition of "Drums." They continued during "Fire on the Mountain." At the end of the performance, the band put up one last homage to Walton -- which stayed up until everyone left the venue.
Walton, of course, was well deserving of the honor -- considering he was truly one of the band's biggest supporters. In his lifetime, it was estimated he attended over 1,000 GD shows -- and after he passed away, Hart called him his "best friend."
We're told the tribute was a special addition to Thursday night's show only ... and will not continue throughout the rest of their Sphere residency.
As we reported, Walton died following a prolonged battle with cancer. He was 71 years old.
RIP.