Gordon Hailwood, waste contracts supervisor for Thames Water, said the 16.5-ton mass was found in the sewers under London Road in Kingston, England.
"While we've removed greater volumes of fat from under central London in the past, we've never seen a single, congealed lump of lard this big clogging our sewers before," Hailwood said. "Given we've got the biggest sewers and this is the biggest fatberg we've encountered, we reckon it has to be the biggest such berg in British history."
The utility said the mass could have led to flooding in homes and on the streets if it had not been removed.
"Homes and businesses need to change their ways, when it comes to fat and wipes, please remember: 'Bin it -- don't block it,'" Hailwood said.