Lancashire all-rounder Liam Livingstone scored 350 off only 138 balls in a club game for Cheshire side Nantwich.
The 21-year-old hit 34 fours and 27 sixes in a National Club Championship match against Caldy.
It is one of the highest one-day scores in history.
"From 100 onwards, I was just trying to whack every ball for six," he told BBC Sport. "When I got into the high 200s and into the 300s, I realised something quite special could happen."
Nantwich made 579-7 before bowling out Caldy for 79 to win by 500 runs.
Livingstone, who is on Lancashire's staff but is yet to play a first-team match, was almost bowled third ball but hit the next delivery for six.
"The wicket was a bit slow and after the fourth ball disappeared I thought I might as well just give it a crack," he said.
"I was just trying to hit almost every ball for six and luckily a few came out of the middle.
"It is all a bit surreal. It hasn't sunk in yet but it is a very proud day and luckily my mum and dad were there to see it."
Livingstone, who made 204 off 242 balls in Lancashire's final second XI game last season against Yorkshire, added: "I have got training with Lancashire at 10 o'clock in the morning, so I will be having an early night.
"But sometime in the near future, I will definitely be having a few drinks to celebrate."