The pants, embroidered with the royal VR monogram, are being sold on behalf of Yesterday's World museum in Sussex.
Auctioneer Richard Edmonds said: "We've been able to date the pants by measuring the waistband and they are from the last 10 years of her life."
The sale also includes nightdresses and stockings worn by Britain's longest-serving monarch and Princess Alice.
The royal intimate apparel - described as in "excellent condition" - is expected to fetch several thousand pounds when it goes under the hammer next week.
Mr Edmonds, from Chippenham Auction Rooms, said he used the "tried-and-tested method" of measuring the waistline to date the underwear to about 1891.
"Earlier in her life she was slimmer but her pants got bigger as she got older," he said.
"As there's such a good photographic record of Queen Victoria, it's possible to calculate her waist measurement over time, so we know roughly when she would have worn items of this size."
According to Mr Edmonds, the 125-year-old underwear was bought by Yesterday's World museum from a descendant of one of Queen Victoria's ladies-in-waiting.
"Items of Queen Victoria's clothing were often given to members of the royal household, particularly after her death in 1901," he said.
"And they're stamped with the royal crest which proves they're from the royal wardrobe."
Also included in the sale on 11 July are stockings and shoes worn by Queen Victoria's third child Princess Alice and replicas of the Crown Jewels.
In 2014, a pair of Queen Victoria's silk bloomers sold at auction in Kent for Â£6,200.

The hashtag #KamiTidakTakut has emerged in the aftermath of Thursday's attacks.
A common meme, of a peace sign with a Jakarta landmark in its centre, was adapted from an image used on social media after the Paris attacks.
Where the Eiffel Tower stood in the Paris version, this shows Indonesia's National Monument.
It stands in the centre of Jakarta as a symbol of the country's struggle for independence. It is a famous landmark and popular meeting point in the city.
A photograph that appeared to show a satay seller continuing to work at his stall after blasts were heard was circulated widely online.
Some Twitter users wrote alongside it: "Fear is not in our dictionary."
The photograph was first uploaded to a local social media site, with a comment saying the stall was 100m away from the site of the bombs, which had happened two hours earlier.
The satay seller has since been interviewed by Indonesian media.
Another popular hashtag was #JakartaBerani, which can be translated as "Jakarta is Brave".
Soon after reports started to filter through on Thursday morning (local time) that explosions had been heard, Twitter users started to use the hashtag #PrayforJakarta. It is not a new hashtag. It had previously been used in cases of severe flooding, but was used again as people from Indonesia and around the world shared their sympathy for the city.
Aulia Masna, a technology blogger in Jakarta, said the morning's events had shown Indonesians used Twitter as much as ever for updates.
He tweeted that "everyone flocks to Twitter", and the microblogging site was not being "abandoned" by Indonesians as some had said.
A pair of Queen Victoria's cotton pants with a 45in (114cm) waistband are to be sold at auction in Wiltshire.
[NEXT_CONCEPT]
People in Jakarta have responded defiantly to the attacks in their city by posting the Indonesian phrase for "We are not afraid" on Twitter.