Lannon has led St. Joseph's since 2003, presiding over expansion plans including the purchase of Episcopal Academy's 38-acre Merion campus, now named for alumnus James J. Maguire. The university is in a dispute with neighbors over its intention to use some of the land for athletic fields. A zoning decision is expected next month, Lannon said.
The school also recently announced plans to build a dormitory for 400 first-year students by July 2012.
St. Joseph's plans to launch a search for a successor.
Lannon, a native Midwesterner and St. Joseph's 26th president, leaves as the university concludes its most ambitious capital campaign. The school has raised $142 million of its $150 million goal, officials said.
Under Lannon, the endowment for the 8,600-student school doubled to its current value of about $148 million.
"I loved being at St. Joseph's," Lannon said, "and I loved being in Philadelphia."
Lannon was in his third three-year contract at St. Joseph's. He will complete the second year of that pact.
The decision to leave was difficult, Lannon said in a statement, adding, "We have accomplished tremendous things, and I know that will continue long after I have left St. Joseph's University."
During his tenure, the university upgraded student housing and other buildings, including Campion Student Center, the Science Center, and the Alumni Memorial Fieldhouse, now known as the Michael J. Hagan '85 Arena. He oversaw the opening of the Pedro Arrupe Center for Business Ethics, the Catholic Bioethics Institute, and the Kinney Center for Autism Education and Support.
He also played a significant role in the growth in the university's academic reputation. Innovations included endowed faculty chairs and student scholarships, and a revised undergraduate curriculum.
This year, Lannon released a 10-year strategic plan for the university.
Paul J. Hondros, chair of the university's board of trustees, said in a statement, "What Father Lannon has brought to St. Joseph's over the past seven years, and continues to bring, cannot be celebrated enough."
Contact staff writer Susan Snyder at 215-854-4693 or email@example.com.