The Terrors were dismantled by Celtic at the weekend as the Scottish champions unleashed a 9-0 thumping - a record home defeat for Dundee.
The former Alloa, St Mirren, Sunderland and Hibernian manager lasted just seven games in charge.
United lost 9-0 to Celtic on Sunday to make it five consecutive defeats and 23 goals conceded in their last four games.
The news of Ross' sacking came on the same day as Scott Parker's departure from Bournemouth after the Cherries also faced a 9-0 defeat to Liverpool in the Premier League.
A club statement read: "Dundee United can confirm head coach Jack Ross has been relieved of his duties with immediate effect.
"Liam Fox will take charge of the the first team on an interim basis with the focus now fully on Wednesday's Premier Sports Cup match with Livingston."
Ross was appointed on June 20 following the departure of Tam Courts to Hungarian side Honved.
The 46-year-old kicked off his reign with a cinch Premiership draw with Kilmarnock and then a 1-0 Europa Conference League win over AZ Alkmaar at Tannadice.
However, after a 1-0 home defeat by Livingston, United went down 7-0 in the Netherlands to equal the worst result by a Scottish club in European competition.
A 4-1 defeat by Hearts and a 3-0 home loss to St Mirren were followed by another capitulation against Celtic.
Ross declared after Sunday's defeat that he was determined to put things right.
"Regardless of what club I'm at or what level I had the same burn to do well as a manager at Alloa as I do now," he said.
"And because of the embarrassment and humiliation I feel right now then, absolutely, I want to put that right."