Murray Chandler, New Zealand's only chess Grandmaster, has donated $35,000 to the Act Party.
The donation was declared under rules requiring donations of more than $30,000 to be disclosed within 10 days of receipt under Section 210 C of the Electoral Act.
Asked about the donation, Act leader David Seymour said he did not play chess very well himself.
"But I know a white knight when I see one.
"He is an outstanding New Zealander and Act is very grateful for his generous support."
Chandler played chess for New Zealand in the 1970s until he was given British citizenship and switched to play for Britain.
He returned to live in New Zealand in 2006 and bought St Pauls Devonport in 2013 to set up the New Zealand National Chess Centre. The centre's website says St Paul's has since been sold again.
In this year's New Year's Honours Chandler was made a Member of the New Zealand Order of Merit for his services to chess.
Alan Gibbs - a regular donor to Act - also recently donated a further $100,000.
Last month, Act held a fundraiser at Antoine's Restaurant featuring Prime Minister Bill English as the keynote speaker, which Seymour said had raised $70,000 for the party's coffers.
The donation disclosures also show The Opportunities Party (TOP) leader Gareth Morgan has shovelled a further $150,000 into the fledgling party, bringing his total donations so far to $400,000 since March.