The prize potato, grown by Peter Glazebrook, tips the scales at a whopping 8lbs 4oz (3.76kg), smashing the previous world record by 9oz.
The vegetable, Peter's Kondor variety, was put on show on Friday at the National Gardening Show in Shepton Mallet, Somerset.
World's biggest potato picture
It is not the first time Mr Glazebrook, 66, from Northampton, has hit the headlines.
The retired chartered surveyor has previously held the world record for the longest carrot, after producing a 17-foot long specimen.
He has also been the double Guinness World Record holder for the heaviest parsnip, at 13lb, and the longest beetroot at 21ft.
Speaking before his latest triumph, he said: ''The secret to success is starting with the right seed.
''It's learning how to grow them and putting a lot of effort in and picking up tips from other growers and reading what you can about it.''
The potato was weighed at the show's Giant Vegetable Competition and Mr Glazebrook is now awaiting verification from Guinness World Records.