It joins Bath, Exmouth, Sidmouth and St Austell in the challenge for the title against towns across the country.
Marlborough Town Council is leading this year's entries into both the RHS South West in Bloom and the Britain in Bloom Competition.
“This is an absolutely fantastic opportunity for Marlborough. It is going to be a challenge, but we have a proactive, experienced team here,” said town mayor Mervyn Hall.
The council is working with members of Marlborough in Bloom and community volunteers to ensure the town will look its best later this year.
"Plans are well under way to make 2020 the best possible entry for the town. We are aiming high,” said Cllr Hall.
“We have a team who are full of ideas and keen to put Marlborough on the map, showcasing the town at its best for the benefit of all who live, work and visit throughout the year. We can do this!”
Now in its 56th year, 70 competition finalists will be going all-out to showcase their horticultural skills, community and environmental efforts.
Marlborough in Bloom first started planting for the competition in 2012.
“We just wanted to see if we could make the town look nicer,” said Marlborough in Bloom’s Richard Beale. For the past three years we have picked up a Gold award, which is amazing, and a real credit to the people who help.”
Last year, Marlborough in Bloom struggled to pull in enough volunteers, but it hopes for a boost following the finalist news.
In Bloom and the town council work closely together. The town team decides on colour schemes and plants and locations, which are then enhanced by Marlborough in Bloom.
“We can ask fire stations and ambulance stations and local business if they want a hanging basket, which adds to the work the council does,” said Richard.
“We use a lot of trailing plants for the baskets and planting begins in early May,” he said.
Each town will be visited by a pair of RHS judges in August as they vie for a medal, a category win and to be named Champion of Champions.
Richard is now also a judge, which means he goes to other areas to provide his expertise to the competition organisers.“It’s a great way to get new ideas.” he said.