Kate wore a red, white and blue sash of the Royal Victorian Order over her white Alexander McQueen gown to the outing, arriving with United States Secretary of the Treasury Steven Mnuchin by her side.
Kate completed her look by accessorizing her classy updo with one of her favorite tiaras (the Lover's Knot tiara), topping it off with the Queen Mother's beautiful sapphire-and-diamond fringe earrings.
Inside the banquet, Kate was also joined by her husband, Prince William, along with Queen Elizabeth II, Prince Charles, Camilla, Duchess of Cornwall, Ivanka Trump, Donald Trump Jr., Eric Trump and Tiffany Trump. At one point, the queen delivered a speech, speaking about the importance of "the close and longstanding friendship between the United Kingdom and the United States."
"As we face the new challenges of the 21st century, the anniversary of D-Day reminds us of all that our countries have achieved together," she said. "After the shared sacrifices of the Second World War, Britain and the United States worked with other allies to build an assembly of international institutions, to ensure that the horrors of conflict would never be repeated. While the world has changed, we are forever mindful of the original purpose of these structures: nations working together to safeguard a hard-won peace."
"Of course, it is not only our security which unites us; but our strong cultural links and shared heritage," she continued. "Every year, there are almost four million visits by Americans to the United Kingdom, with a great number claiming British descent. And with your own Scottish ancestry, Mr. President, you too have a particular connection to this country."
See more pics from the evening, shared via The Royal Family Twitter account, below:
As for Harry's wife, Meghan Markle, ET reported last week that she would not be attending any of the events scheduled during Trump's three-day visit of the U.K. While Kensington Palace did not release a statement regarding her reason for skipping out, the Duchess of Sussex -- who just gave birth to son Archie on May 6 -- famously criticized Trump in 2016, calling him "divisive" and "misogynistic" in an interview on The Nightly Show With Larry Wilmore.
When Trump was reminded of Meghan's comments by The Sun on Saturday, he said he was unaware they were made. "So, what can I say? I didn't know that she was nasty," he told the outlet.
Regardless, Trump did have some nice words for Meghan during the interview. "I hope that she's OK," he said, referring to her being on maternity leave, adding that he thinks it's "nice" to have an American in the royal family.
"I'm sure she will do excellently," he said. "She'll be very good. I hope she does."