Celebrity chef Jamie, wooed model turned fashion designer Jools, with love letters before they dedicated their lives to each other at All Saints Church in Rickling Green, Essex on 24 June 2000.
The couple - who are parents to Poppy Honey, 16, Daisy Boo, 15, Petal Blossom, nine, Buddy Bear, seven, and one-year-old River Rocket - poured their admiration for each other into lengthy Instagram posts shared on Sunday night, revealing that they are just as giddy about one another as they were as loved-up teens.
Mother-of-five Jools said: "Happy happy anniversary my soul mate, the person I want to wake up to every morning. The person who still makes my heart skip a beat when I see his name on my phone. When I really need you, you are there when I am scared you reassure me and when I am tired you make me a dam good cup of coffee!!!! You would do anything for us and most of all you make me feel safe. Love you more than all these words xxx".
Jamie wrote: "Today I am so proud to celebrate my 18 wedding anniversary with this amazing woman!! Thank you so much for being my soul mate on this most bonkers roller coaster ride called life, what a journey it's been so far. Thank you for being by my side, thank you for seeing things I never see, thank you loving me, for being the best wife & most fantastic mother of our 5 precious children....I LOVE YOU SO MUCH....now stop watching love island and come find me in the garden waiting to give you your anniversary pressie....hurry up!!! Love jamie ox x x x x".
Both posts prompted a flood of congratulations from followers and fans, with many citing the OIivers' relationship as their "marriage goals".
One person wrote: "Marriage role models".
Another said: "Congratulations, enjoy your special day together and many more years to come."
The couple, who live in London and share glimpses of their daily family life on social media. have shared their anniversary with followers previously - offering some insight into the early days of their relationship as teenage sweethearts.
The down to earth couple tied the knot when they were both age 25, as Jamie who now has 6.4m followers on Instagram began rising in prominence for his cooking skills.