The holder of the winning ticket - bought in Worcester for the 9 January draw - has opted to remain anonymous.
About £66m had been up for grabs to players, but it was the unclaimed £33,035,323 that had people checking their old tickets.
In the days since the winning numbers were announced, Camelot has been inundated with claims.
Camelot said the fact that a ticket had been validated within 180 days of the draw meant it had not been submitted under its lost, stolen destroyed or damaged policy.
One woman, who bought a ticket in Worcester, had sought to verify whether hers was the winner after putting it through the wash, damaging its identifying barcode.
A Camelot spokesperson said: "It would have been awful if the ticket-holder had missed out on this substantial and life-changing amount of money. We would like to remind all National Lottery players to check their tickets every time they play."
The operator has been processing "hundreds of claims" of stolen, lost or destroyed tickets.
The prize money is half the record Lotto jackpot win - shared with a couple from Hawick who claimed their prize within days of the 9 January draw.
On Tuesday, Camelot warned it would take action against any fraudulent claimants.
The winning numbers were 26, 27, 46, 47, 52 and 58.
Timeline
UK lottery operator Camelot has received a "valid claim" for a record £33m Lotto jackpot prize, it says.