Yang Guang received special gifts, including a giant box of his favourite bamboo and sticky honey smeared on rocks and branches around his enclosure.
The Zoo's 20.5-stone star attraction was also presented with a panda cake, made from a special recipe from China and topped with carrots for candles.
Birthday cards were sent to his home from his fans around the globe while groups of followers showed up to wish him a happy birthday in person.
Darren McGarry, Head of Living Collections at the Zoo, said: "This is Yang Guang's 19th birthday and he's taking it easy these days.
"He usually spends around eight hours per day eating and another eight or nine hours sleeping, but we've got some special treats in store for his birthday.
"But there are panda fans all around the world. Yang Guang always gets lots of birthday cards so we'll be putting these on show in the panda house.
"People have even been known to buy gifts from the Zoo's Amazon wish list and send big containers of honey."
Giant panda Yang Guang -- meaning Sunshine -- was born on 14 August 2003 at the Bifengxia Panda Breeding Centre in China.
He arrived in Scotland on an initial ten year loan along with a female named Tian Tian -- or Sweetie -- in December 2011, costing £600,000 per year.
It was hoped that the pair would produce a cub in Scotland and, after failing to breed naturally, Tian Tian was artificially inseminated from 2013, without success. Efforts were halted during lockdown restrictions.
Yang Guang was diagnosed with testicular cancer in 2018, and later castrated after the disease was detected in both testicles. Subsequent tests have shown he is now cancer free.
Last year, the RZSS negotiated a two year extension to the loan deal, which will allow the pair to remain in Scotland until the end of 2023.
McGarry said there would be no further attempts to produce a cub, however, and no further extensions to the animals' stay in Scotland.
He said: "Our giant pandas were brought to Scotland because we wanted to support the conservation of the species and educate people and we've achieved that.
"Both will go back to China at the end of 2023. No further attempts at breeding will take place and we will just enjoy having Yang Guang and Tian Tian with us for their remaining time at Edinburgh Zoo.
"They are amazing animals and they will be missed but there's still lots of time to see them before they go back to China."
The female, Tian Tian, will celebrate her 19th birthday on August 24.