Kate was greeted by AELTC Chairman Philip Brook and his wife Gill.
The Brooks have been familiar faces at the tournament for years, but that is set to change soon as Mr Brook is to step down and hand over the reigns to Ian Hewitt in the coming months.
The Duchess arrived with Pippa over an hour before the match got underway to meet players, volunteers and former champions in her role as patron.
An arrival video.
It marks Kate's second visit to the tournament this year. Last week, the Duchess enjoyed a day of courtside action for the second day of the championships. During the visit, she met Andy Murray, who made a valiant return to Wimbledon to play mixed doubles with Serena Williams (I would have loved to see the dynamic duo make it to the final). Kate watched British wildcard Harriet Dart, before Angelique Kerber took on Tatjana Maria, and Roger Federer won his first-round match. Tomorrow, Kate will be joined by William to watch Federer take on Novak Djokovic in the final.
Kate, Meghan and Pippa take their seats in the Royal Box on Centre Court.
Serena Williams entered today's match knowing it could be a history-making day for her career. A win would have seen the American tennis star secure her 24th Grand Slam singles title, tying with Margaret Court, the only other player to have reached that number. Williams was also competing for her eighth Wimbledon singles title. On the other side of the court, Romanian player Simona Halep was ready to fight for her first singles title at the iconic tournament. After her French Open win in 2017, Halep has been striving for her next major victory. Ahead of the match she said: "I feel mentally strong. We will see what happens."
Ahead of the final, Halep said she would love it if patron Kate attended the final.
Last year, Kate and Meghan attended the women's final together for the first time. Kate had given birth to Louis less than three months previously, and it was just weeks after Harry and Meghan's wedding.
This year, Louis is over a year old and Meghan is mom to two-month-old Archie. It's amazing how much can change in a year.
The trio watch a tense first set.
Meghan and Pippa were photographed laughing and exchanging smiles on several occasions. Meghan attended the evening reception of Pippa's wedding when she was dating Harry, and last year Pippa and the Middleton family attended the Sussexes' Windsor wedding.
The two sisters-in-law were together earlier this week for a polo match with their children. Given their shared love of tennis, it was great to see them team up again today.
An overview of Centre Court.
From the off, Halep took command of the game and displayed incredible tennis skill. She won in straight sets - her first Wimbledon title.
More from Wimbledon:
'History wastes no time listening to those who speak of what is likely to happen. History heeds only those who make it happen – and in the women’s final at Wimbledon 2019, Simona Halep wrote her own name large. The No.7 seed, whose name appeared on no one’s list of likely winners before The Championships began, became the first Romanian ever to win a Wimbledon title.
She stunned Serena Williams, the Centre Court crowd and almost everyone on Planet Tennis to triumph 6-2, 6-2 in just 55 minutes, with a display so resourceful, so near-flawless that there could be no answer.
Two-and-a-half long years after Williams secured her 23rd Grand Slam title at the 2017 Australian Open, this toweringly remarkable woman found she must wait still longer for the elusive 24th crown to equal Margaret Court’s all-time record.
Twelve months ago Angelique Kerber defied her here; few could envisage Halep stonewalling Williams again on the same court – yet she did. In this battle of the former world No.1s, history was written, and history was denied; and the whole was utterly thrilling.'
Applause after the match.
Kate and Meghan talking after the match ended.
Kate placed her hand on Meghan's back, I imagine commiserating with her over Serena's loss. It was a very sweet moment between the pair.
Following her win Simona Halep said: "Thank you for coming everyone from the Royal family." She added she didn't know she would be meeting Kate but added it was "amazing".
Cheers from Pippa!
An overview before Serena and Simona left the court.
It looks like all three ladies had a wonderful afternoon. They all adore tennis, and with Kate's role as patron, Meghan's friendship with Serena, and Pippa's love of the sport, it was an ace day out all round!
From the Kensington Palace Instagram account "The Duchess of Cambridge, Wimbledon Patron, and The Duchess of Sussex attended the Wimbledon 🎾 Ladies’ Singles Final today. Well done to Serena Williams and Simona Halep on a fantastic match, and congratulations Simona on your first Wimbledon title!"
In the video below shared by Gert's Royals, Kate congratulates the champion.
.@Simona_Halep greeted by her mother & Duchess Kate, Patron of @Wimbledon after being presented with the trophy. pic.twitter.com/ENcMCb0HPL— Gert's Royals (@Gertsroyals) July 13, 2019
Kate brought back her her bottle green Dolce & Gabbana Crépe Embellished Dress. Kate first wore the piece during the 2016 Canada tour. The vivid green hue is gorgeous.
The bottle-green dress features gold-toned buttons down the front, a bow-tie collar, and a ruffled trim along the sleeve seals. The decorative pocket watch detailing is an eye-catching addition to the dress; it's crafted of sequin, crystal, and gold-beaded pocket-watch appliqué.
Kate accessorised with her $1,695 Dolce & Gabbana Pink Medium Miss Sicily Bag, described as: "Structured grained 'dauphine' calfskin top handle bag in 'rose' pink. Carry handle at top. Adjustable and detachable shoulder strap with lobster clasp fastening." She carried the piece for Wimbledon last year. It's available at Harrods.
The Duchess accessorised with her Asprey Oak Leaf earrings.
It appears Kate wore her Rupert Sanderson Malory pumps in nude.
And her Ray Ban Wayfarer sunglasses. They are available at Nordstrom.
Anna Mason London Ruflette Sleeveless Midi Dress. The liberty blue flower print dress is available for pre-order for £735.
For details on what Meghan wore, pop over to Mad About Meghan.
We'll see William and Kate for the men's final tomorrow at 2 pm.