Anthony Bamford is the multimillionaire founder of JCB, a firm which produces construction and agriculture equipment and is best known for its bright yellow diggers.
The company has worked closely with the UK government in recent years and has donated to a number of Conservative politicians.
Bamford donated £20,000 personally to Johnson's campaign as well as a further £41,000 through his business.
Earlier this year, the firm paid Johnson £10,000 three days before he gave a speech in which he repeatedly praised the company.
In his speech, Johnson said that "nothing and no one will stop [JCB's] spread" and called on politicians to "emulate the spirit of JCB".
Speaking to the Sun newspaper earlier in June, Bamford said that "Boris has what it takes to be a remarkable Prime Minister at a pivotal moment in our history.
"He'll get Brexit over the line. He'll keep old-fashioned socialism out of No. 10 – and hold back that particular threat to our prosperity."