Isidore Mörsel, president of the Antwerp World Diamond Centre (AWDC), presented the ring this week to US Ambassador Bill White on behalf of the city's centuries-old diamond community.
"May this ring serve as a lasting reminder that true partnership, like the finest natural diamonds, is formed under pressure, endures the test of time and shines brightest when built on trust," Mörsel said.
The gift follows the US decision to lift tariffs on more than $USD2 billion ($AUD2.8 billion) in annual polished diamond exports from Antwerp. The 18-carat gold ring contains 321 diamonds, 56 sapphires, 13 emeralds and six rubies.
It displays Trump's initials, the numbers 45 and 47, patriotic US symbols and an interior engraving that reads, "Crafted in Antwerp for Donald John Trump". Antwerp jeweller David Gotlib designed the ring.
The ring was unveiled at a Brussels event attended by more than 8,000 guests. In a video message during an event, Trump said: "A very special thank you to my friends from Antwerp for the magnificent Freedom 250 ring".
According to The Associated Press, US ethics experts described Trump's acceptance of the ring as a departure from long-standing White House practice. Unlike gifts from foreign governments, personal gifts to US presidents are not subject to constitutional restrictions.
Ambassador White is expected to deliver the ring to Trump, after which it will be displayed in the Oval Office.
More reading
Global tariff saga returns with new Trump proposal
Trump tariff saga continues with refund controversy
Supreme Court strikes down Trump tariffs
Ethics uproar after government official promotes jewellery
Rolex dragged into US political feud after Trump meeting