It will provide flowers, cake, outfits, a humanist wedding celebrant and a “first class wedding breakfast”.
The wedding on August 10 will last nearly four-and-a-half hours, while the train makes a return trip from London Euston to Birmingham New Street.
Many engaged couples have seen plans for their big day disrupted during the coronavirus pandemic.
But there will be no limit on the number of guests at weddings in England from Monday.
Avanti West Coast’s executive director of customer experience Natasha Grice said: “With the wedding industry and married couples-to-be having a tough time over the past year and a half, we couldn’t think of a better way to mark everyone coming together again than helping one lucky couple celebrate with their loved ones, onboard the Avanti West Coast marriage carriage.
“Encourage your friends and family to enter online. We want to hear their stories, and ensure the winning couple have the wedding celebration they’ve missed out on.”
The competition runs until July 26.
Interested couples should visit here to answer questions about their circumstances and why they deserve the prize.
The winning couple will be selected based on their responses.