Jonathan Mariner
General Partner, Chief Financial Officer
Jonathan Mariner is a seasoned business executive, investor, and technology entrepreneur, currently serving as a General Partner at Harbinger Sports Partners Fund I, LP, where he helps lead investment strategies focused on innovation across the sports, media, and entertainment landscape. With a distinguished track record in finance, operations, and digital transformation, Mariner brings deep institutional and entrepreneurial insight to the fund’s portfolio strategy.
Executive Leadership in Sports & Finance
Mariner spent over a decade at Major League Baseball (MLB), where he served as Chief Financial Officer before becoming the league’s first-ever Chief Investment Officer. As CFO, he oversaw the financial operations of all 30 clubs, driving fiscal discipline, revenue growth, and large-scale strategic initiatives. He was later tapped to lead MLB’s investment strategy, managing the league’s private equity interests and evaluating opportunities across emerging tech, media, and fan engagement platforms.
Before joining MLB, Mariner held senior financial roles at several MLB clubs, including the Florida Marlins and the Montreal Expos. He also served as Vice President and CFO of the Beacon Council, Miami-Dade County’s economic development agency.
Entrepreneurship & Innovation
After his tenure in professional sports, Mariner founded TaxDay, a location-tracking app that helps individuals and businesses manage state residency and tax exposure. The app reflects his commitment to creating tech-driven solutions to real-world problems and has earned acclaim among high-net-worth individuals, athletes, and advisors alike.
Mariner is also a sought-after advisor and board member, having served on the boards of Learfield, Arctos Sports Partners, and several sports and entertainment ventures. He is widely respected for his ability to navigate the complex intersections of sports business, finance, and innovation.
Education & Personal Life
Mariner holds an MBA from Harvard Business School and a bachelor’s degree in accounting from the University of Virginia, where he later served on the Board of Visitors. A strong advocate for diversity and mentorship in business, he supports programs that expand access to opportunities in sports, finance, and entrepreneurship.
He resides in New York and Florida and enjoys mentoring young entrepreneurs, exploring new technologies, and spending time with his family.
Our Team
The Harbinger team brings an unprecedented assembly of sports ownership experience, operational expertise, and financial innovation
Jonathan Mariner
General Partner, Chief Financial Officer
Jonathan Mariner is a seasoned business executive, investor, and technology entrepreneur, currently serving as a General Partner at Harbinger Sports Partners Fund I, LP, where he helps lead investment strategies focused on innovation across the sports, media, and entertainment landscape. With a distinguished track record in finance, operations, and digital transformation, Mariner brings deep institutional and entrepreneurial insight to the fund’s portfolio strategy.
Executive Leadership in Sports & Finance
Mariner spent over a decade at Major League Baseball (MLB), where he served as Chief Financial Officer before becoming the league’s first-ever Chief Investment Officer. As CFO, he oversaw the financial operations of all 30 clubs, driving fiscal discipline, revenue growth, and large-scale strategic initiatives. He was later tapped to lead MLB’s investment strategy, managing the league’s private equity interests and evaluating opportunities across emerging tech, media, and fan engagement platforms.
Before joining MLB, Mariner held senior financial roles at several MLB clubs, including the Florida Marlins and the Montreal Expos. He also served as Vice President and CFO of the Beacon Council, Miami-Dade County’s economic development agency.
Entrepreneurship & Innovation
After his tenure in professional sports, Mariner founded TaxDay, a location-tracking app that helps individuals and businesses manage state residency and tax exposure. The app reflects his commitment to creating tech-driven solutions to real-world problems and has earned acclaim among high-net-worth individuals, athletes, and advisors alike.
Mariner is also a sought-after advisor and board member, having served on the boards of Learfield, Arctos Sports Partners, and several sports and entertainment ventures. He is widely respected for his ability to navigate the complex intersections of sports business, finance, and innovation.
Education & Personal Life
Mariner holds an MBA from Harvard Business School and a bachelor’s degree in accounting from the University of Virginia, where he later served on the Board of Visitors. A strong advocate for diversity and mentorship in business, he supports programs that expand access to opportunities in sports, finance, and entrepreneurship.
He resides in New York and Florida and enjoys mentoring young entrepreneurs, exploring new technologies, and spending time with his family.
Jonathan Mariner
General Partner, Chief Financial Officer
Jonathan Mariner is a seasoned business executive, investor, and technology entrepreneur, currently serving as a General Partner at Harbinger Sports Partners Fund I, LP, where he helps lead investment strategies focused on innovation across the sports, media, and entertainment landscape. With a distinguished track record in finance, operations, and digital transformation, Mariner brings deep institutional and entrepreneurial insight to the fund’s portfolio strategy.
Executive Leadership in Sports & Finance
Mariner spent over a decade at Major League Baseball (MLB), where he served as Chief Financial Officer before becoming the league’s first-ever Chief Investment Officer. As CFO, he oversaw the financial operations of all 30 clubs, driving fiscal discipline, revenue growth, and large-scale strategic initiatives. He was later tapped to lead MLB’s investment strategy, managing the league’s private equity interests and evaluating opportunities across emerging tech, media, and fan engagement platforms.
Before joining MLB, Mariner held senior financial roles at several MLB clubs, including the Florida Marlins and the Montreal Expos. He also served as Vice President and CFO of the Beacon Council, Miami-Dade County’s economic development agency.
Entrepreneurship & Innovation
After his tenure in professional sports, Mariner founded TaxDay, a location-tracking app that helps individuals and businesses manage state residency and tax exposure. The app reflects his commitment to creating tech-driven solutions to real-world problems and has earned acclaim among high-net-worth individuals, athletes, and advisors alike.
Mariner is also a sought-after advisor and board member, having served on the boards of Learfield, Arctos Sports Partners, and several sports and entertainment ventures. He is widely respected for his ability to navigate the complex intersections of sports business, finance, and innovation.
Education & Personal Life
Mariner holds an MBA from Harvard Business School and a bachelor’s degree in accounting from the University of Virginia, where he later served on the Board of Visitors. A strong advocate for diversity and mentorship in business, he supports programs that expand access to opportunities in sports, finance, and entrepreneurship.
He resides in New York and Florida and enjoys mentoring young entrepreneurs, exploring new technologies, and spending time with his family.
Jonathan Mariner is a seasoned business executive, investor, and technology entrepreneur, currently serving as a General Partner at Harbinger Sports Partners Fund I, LP, where he helps lead investment strategies focused on innovation across the sports, media, and entertainment landscape. With a distinguished track record in finance, operations, and digital transformation, Mariner brings deep institutional and entrepreneurial insight to the fund’s portfolio strategy.
Executive Leadership in Sports & Finance
Mariner spent over a decade at Major League Baseball (MLB), where he served as Chief Financial Officer before becoming the league’s first-ever Chief Investment Officer. As CFO, he oversaw the financial operations of all 30 clubs, driving fiscal discipline, revenue growth, and large-scale strategic initiatives. He was later tapped to lead MLB’s investment strategy, managing the league’s private equity interests and evaluating opportunities across emerging tech, media, and fan engagement platforms.
Before joining MLB, Mariner held senior financial roles at several MLB clubs, including the Florida Marlins and the Montreal Expos. He also served as Vice President and CFO of the Beacon Council, Miami-Dade County’s economic development agency.
Entrepreneurship & Innovation
After his tenure in professional sports, Mariner founded TaxDay, a location-tracking app that helps individuals and businesses manage state residency and tax exposure. The app reflects his commitment to creating tech-driven solutions to real-world problems and has earned acclaim among high-net-worth individuals, athletes, and advisors alike.
Mariner is also a sought-after advisor and board member, having served on the boards of Learfield, Arctos Sports Partners, and several sports and entertainment ventures. He is widely respected for his ability to navigate the complex intersections of sports business, finance, and innovation.
Education & Personal Life
Mariner holds an MBA from Harvard Business School and a bachelor’s degree in accounting from the University of Virginia, where he later served on the Board of Visitors. A strong advocate for diversity and mentorship in business, he supports programs that expand access to opportunities in sports, finance, and entrepreneurship.
He resides in New York and Florida and enjoys mentoring young entrepreneurs, exploring new technologies, and spending time with his family.
Jonathan Mariner
General Partner, Chief Financial Officer
Jonathan Mariner is a seasoned business executive, investor, and technology entrepreneur, currently serving as a General Partner at Harbinger Sports Partners Fund I, LP, where he helps lead investment strategies focused on innovation across the sports, media, and entertainment landscape. With a distinguished track record in finance, operations, and digital transformation, Mariner brings deep institutional and entrepreneurial insight to the fund’s portfolio strategy.
Executive Leadership in Sports & Finance
Mariner spent over a decade at Major League Baseball (MLB), where he served as Chief Financial Officer before becoming the league’s first-ever Chief Investment Officer. As CFO, he oversaw the financial operations of all 30 clubs, driving fiscal discipline, revenue growth, and large-scale strategic initiatives. He was later tapped to lead MLB’s investment strategy, managing the league’s private equity interests and evaluating opportunities across emerging tech, media, and fan engagement platforms.
Before joining MLB, Mariner held senior financial roles at several MLB clubs, including the Florida Marlins and the Montreal Expos. He also served as Vice President and CFO of the Beacon Council, Miami-Dade County’s economic development agency.
Entrepreneurship & Innovation
After his tenure in professional sports, Mariner founded TaxDay, a location-tracking app that helps individuals and businesses manage state residency and tax exposure. The app reflects his commitment to creating tech-driven solutions to real-world problems and has earned acclaim among high-net-worth individuals, athletes, and advisors alike.
Mariner is also a sought-after advisor and board member, having served on the boards of Learfield, Arctos Sports Partners, and several sports and entertainment ventures. He is widely respected for his ability to navigate the complex intersections of sports business, finance, and innovation.
Education & Personal Life
Mariner holds an MBA from Harvard Business School and a bachelor’s degree in accounting from the University of Virginia, where he later served on the Board of Visitors. A strong advocate for diversity and mentorship in business, he supports programs that expand access to opportunities in sports, finance, and entrepreneurship.
He resides in New York and Florida and enjoys mentoring young entrepreneurs, exploring new technologies, and spending time with his family.