The classical singer looked beautiful in blue at a showing of Andrew's directorial debut Lullaby on Wednesday night (11 June).
Katherine, 33, posed for photographers with a hand on her man's shoulder, giving us all a very good glimpse at that rock!
The former Dancing With The Stars contestant became engaged to 36-year-old Andrew in April, after they reportedly began dating the previous October.
She confirmed Andrew's proposal via Twitter, telling fans: "Thank you for all your lovely wishes of congratulations. They mean so much to us."
Andrew joined Katherine at Buckingham Palace earlier this year, where she collected an OBE. It was their first public appearance together.
Last night, Katherine looked as proud as could be while supporting Andrew at his film premiere. Lullaby stars Amy Adams, Garrett Hedlund and Jennifer Hudson. It focuses on a man who is estranged from his family then learns his dad has chosen to take himself off life support within the next 24 hours.
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Celebrities who became engaged in 2014 in pictures:
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