John Bernard O'Brien (31 July 1925 – 12 October 1990) was a political candidate and party leader of Social Credit in New Zealand.

Following the sudden death of Bill Brown, O'Brien unsuccessfully contested the Palmerston North electorate in the 1967 by-election.

[4] Although a powerful speaker and an energetic organiser, O'Brien was accused by his opponents of being abrasive and overly confrontational.

[6] He later sued the Social Credit Party for defamation regarding a statement of claim against him in an article published in The Nelson Mail in 1972.

A four and a half day trial was held at the Nelson courthouse where the jury found against O'Brien's $50,000 case, determining that the words in the article in question were not published to readers with authority from the party and nor did the paper infer that it was.