The Hereditary Grand Duke, 32, who wed Countess Stephanie de Lannoy in October 2012, poses in a smart navy suit alongside his 30-year-old princess.
Dressed in a glittering beige dress, adorned with jewels, Stephanie looks every inch the elegant royal.
In one charming black-and-white shot, Prince Guillaume laughs uproariously while Stephanie cracks a broad smile.
The new pictures of Guillaume and Stephanie come just under two weeks after the prince became an uncle for the third time.
Guillaume's brother Prince Félix and his wife Princess Claire welcomed a daughter called Princess Amalia Gabriela Maria Teresa on 15 June.
Princess Amalia is Guillaume's first niece. The future Grand Duke has two nephews, Gabriel, eight, and Noah, six, whose parents are his brother Prince Louis and his wife Princess Tessy.