Barcelona: Martini will be ending its title sponsorship of Williams at the end of the season and leaving Formula One, the team`s deputy principal Claire Williams said on Tuesday.
The partnership between the drinks brand and former world champions is entering its fifth year and had been up for renewal.
"Martini is leaving us at the end of this year," Williams told reporters during Formula One testing at the Circuit de Catalunya.
"It's the end of their contract and we have been in discussions with them for many months now about an extension beyond 2018.
"They are withdrawing not just from Williams but the whole of Formula One, so you won't see them on another team in 2019," she added.
Williams, a family-owned team who won nine constructors championships between 1980 and 1997, last won a race in 2012 and major sponsors like Martini make an important contribution to the overall budget.
Claire Williams said it was important to have the resources to go racing but that might not mean looking for another title partner.
"We are financially stable at the moment and we are not unduly concerned about them leaving," she added.
There have been some drawbacks with the Martini deal, however, with alcohol regulations limiting the use of under-25 drivers in some jurisdictions.
Williams has the youngest lineup in Formula One, with 19-year-old Canadian Lance Stroll and 22-year-old Russian Sergey Sirotkin.
The former is the son of a billionaire and the other is backed by an oligarch with close ties to Russian president Vladimir Putin.
The team also have Poland's Robert Kubica, 33, as the reserve and 25-year-old Briton Oliver Rowland as an "official young driver".
Williams said Martini had been fully supportive of the driver choice and that had not been a factor in Martini's decision.
"I suppose next year it gives us the freedom to do what we need to do without having to worry about any age limit," she added.
Most Formula One teams have struggled to attract sponsors of late and Williams said brands had a far greater choice of marketing platforms available now.
"I do think Formula One probably needs to work harder as a collective," she added.
"We went through a really wonderful period where this was the ultimate for putting your marketing campaigns. I think we probably do need to work a bit harder to make sure we`re delivering for all partners that come into this sport."