Source: Sharecast
While he will continue to own a stake in the business, Hargreaves - who set up the firm in 1981 - will hand his board position to his son Robert.
HL said Hargreaves had rejoined the board earlier this year "to provide continuity and support through a period of change" but has decided the time was now right to retire.
Hargreaves Lansdown said its co-founder will "maintain a close relationship" with the company and "has offered to make his insight and experience available if needed".
Peter Hargreaves said: "Hargreaves Lansdown is a company I have loved ever since its formation in 1981 and after the takeover, I felt it was important that I had close contact with the business.
"I have been greatly impressed by the strength and direction of the team now leading the business and I am confident it is now well-placed for future success.
"The appointment of Robert marks a proud new chapter in the family legacy and at 79 years of age, I look forward to enjoying a little more time in foreign sunshine and tending to my garden."