He joins the London-based short and medium-term lender from Fidelity Worldwide Investors, where he was director.
Harris has been chief operating officer of Pyramis Global Advisors UK, Fidelity’s institutional asset management company.
He said: “For me, this is a fantastic opportunity to join a highly entrepreneurial and fast-growing market leader in a sector that is thriving.
“Dragonfly has established itself as the major force within short term lending and my role, which I am relishing, is to help it scale for continued growth and increased market share."
While at Pyramis, he grew funds under management to £2.5bn in five years by building the distribution, investment research and investment management functions.
Jonathan Samuels, chief executive officer of Dragonfly Property Finance, added: “In hiring Marc we have made our plans for Dragonfly very clear. The market we are in still has a huge amount of potential.
“However, to continue to grow we need to scale up and Marc will be working alongside our existing management team of Mark Posniak, Matt Smith and Ludo Mackenzie to make this happen.
“The majority of Marc's working career has been in large corporates and he is acutely aware of the challenges we will face as we grow, and the systems we need to embed in order to operate efficiently."
