Kate wore a couture creation by British designer Phillipa Lepley, with a striking full-length, champagne gold hand-embroidered Chantilly lace evening coat featuring a regal-looking high collar over a silk crepe gown.
Trump made a point of referencing the princess, who announced at the start of 2025 she was in remission from cancer, in his banquet speech, describing her as "so radiant and so healthy and so beautiful".
The princess was seated next to the US president at the banquet table and was seen smiling up at him as he delivered his speech.
"His Majesty has also raised a remarkable son in His Royal Highness, the Prince of Wales. Really amazing," Trump said.
"We've gotten to know you and I think you're going to have an unbelievable success in future.
"Melania and I are delighted to visit again with Prince William and to see Her Royal Highness, Princess Catherine, so radiant and so healthy, and so beautiful. It's really a great honour, thank you."
Kate beamed as she stood and raised her glass to toast the president after he addressed the 160 guests in Windsor Castle's St George's Hall.
Her delicate coat featured hand-embroidered roses with couched gold cording, accented with French knots and satin-stitched blooms, demonstrating her commitment to supporting British craftsmanship and creativity.
Kate's earrings belonged to the late Queen and the princess opted for her go-to tiara, the Lover's Knot Tiara, and wore her hair down and styled in waves.
Earlier in the day, Trump appeared to tell future queen, Kate, "You're so beautiful, so beautiful" as she greeted him and the first lady Melania Trump with the Prince of Wales at the start of the state visit.
The princess played a key role during the royal charm offensive deployed towards the US leader as she was tasked along with William as being the first to meet the Trumps from Marine One on Wednesday morning, walking with him to see the King and Queen.
Heir to the throne William and Kate also held a "warm and friendly" private meeting with the Trumps in Windsor Castle after lunch.
The engagement had not been previously announced as part of the official schedule.
At the banquet Melania Trump opted for a fitted, more daring off-the-shoulder, long-sleeved vivid yellow gown, with contrasting wide pink buckled belt.
The Queen was wearing a royal blue silk marocain embroidered dress by Fiona Clare, and a sapphire and diamond tiara.
William was in a white tie and a Windsor tail coat, and a ceremonial sash and badge, along with a number of miniature medals.
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