Kate Middleton and Prince William have kicked off their three-day tour of the US, their first trip stateside in eight years.

The trip is a significant one for the pair as it's their first since becoming Prince and Princess of Wales and the first since the passing of the Queen. It will culminate with the Earthshot Prize on 1 December, a glamorous event honouring those making a positive impact on the environment.

The couple touched down in Boston yesterday afternoon, where they were greeted by Massachusetts Governor Charlie Baker, First Lady of Massachusetts Lauren Baker and Lieutenant Governor Karyn Polito.

Photo: Getty

Their first stop was to City Hall, where they met Boston's Mayor Michelle Wu and her family. William later delivered a speech on why he brought the Earthshot Prize ceremony to Boston for its second year.

"Sixty years ago, President John F. Kennedy's "Moonshot" speech laid down a challenge to American innovation and ingenuity. 'We choose to go to the moon,' he said, 'not because it is easy but because it is hard.’

"Like President Kennedy, Catherine and I firmly believe that we all have it in ourselves to achieve great things and that human beings have the ability to lead, innovate and problem-solve." The couple then assisted in lighting up City Hall in green.

Kate's outfit was also on theme as she chose an elegant green tartan dress and matching bottle green coat, both by classic British designers.

Her dress was by Burberry and featured a high neckline, asymmetric draping in the front and long sleeves in a rich dark green tartan print, flecked with red and white for a subtly festive feel. It appeared to be a custom design based on the 'Aurora' dress, and used the same pattern seen on Burberry's Tartan Kilt.

She paired it with a long green coat by Alexander McQueen, a firm favourite of hers.

Photo: Getty

She accessorised with a new bag, the Amberley Small Satchel by Mulberry, which features a fold over top, a Rider's lock, and gold hardware borrowed from equestrian styling. She finished her look with the Emmy London Rebecca in a colour called greenery.

Kate added a touch of sparkle with pearl drop earrings by Shyla London, the Chunky Knot Baroque Pearl style.

Later that night, Kate changed into a new outfit for the couple's visit to the Boston Celtics game against the Miami Heat.

Photo: Getty

She wore her midnight blue Chanel blazer, a vintage piece dating from 1995 which features notched lapels, patch pockets, turned-back cuffs, and contrasting trim. She paired it with black skinny jeans and black suede Gianvito 105 pumps.

She accessorised with a classic chunky gold necklace, the Laura Lombardi Portrait 14kt Gold-Plated Chain Necklace, and the Biaritz Squiggle Earrings also by Shyla London.