CHESAPEAKE, Va. — Gary Philbin has been named president and chief executive officer of Dollar Tree Inc.

The move is part of a planned leadership succession in which Bob Sasser, the company’s CEO since 2004, has assumed the role of executive chairman of the board.

Sasser, 65, joined Dollar Tree in 1999 as chief operating officer. He was promoted to president and chief operating officer in 2001, and to president and CEO in 2004.

During Sasser’s tenure, Dollar Tree has grown from a company with fewer than 1,200 stores and less than $1 billion in annual sales to one with more than 14,500 retail stores and projected 2017 revenues of more than $22 billion. Dollar Tree completed six acquisitions during Sasser’s time as CEO, including the $9.1 billion acquisition of Family Dollar Stores Inc. in 2015. Dollar Tree’s market capitalization has grown from approximately $2.3 billion to $19.8 billion during this time.

“I am extremely proud of our company and especially the 180,000 associates that work hard, delivering value and convenience to millions of customers every day,” Sasser said in a statement. “Our people make Dollar Tree and Family Dollar stores among the best retailers in North America. We have built a solid and scalable infrastructure. We have room to grow and tremendous opportunities to serve more customers in more ways, while increasing returns for our long-term shareholders. Our company’s future has never been brighter!”

Effective Monday, Philbin was promoted from his prior post of enterprise president to succeed Sasser as president and chief executive officer of Dollar Tree, and was also appointed to the company’s board.

Philbin, 60, joined Dollar Tree in 2001 as senior vice president of stores. He was promoted to chief operating officer in 2007, and to president and chief operating officer in 2013. He assumed the role of president and chief operating officer of Family Dollar upon its acquisition by Dollar Tree in July 2015, and in January of this year he was promoted to enterprise president with responsibilities for both Dollar Tree and Family Dollar banners.

“Gary has been a tremendous business partner to me for the past fifteen years,” Sasser said. “We share the same values, have a common vision for Dollar Tree’s future, and are aligned on strategic initiatives and priorities to achieve the Company’s business goals. Succession planning has been an important part of Dollar Tree’s organizational efforts and culture for many years. Working with our board of directors, I have been planning leadership succession for some time and we are confident this will be a seamless transition, both inside and outside of the company. Our board of directors and leadership team have complete confidence in Gary’s ability to lead Dollar Tree through its next phases of growth.”

Philbin praised Sasser for his leadership.

“Bob has led Dollar Tree to industry-leading returns for shareholders and success for all of our stakeholders,” Philbin said. “Bob’s vision has transformed Dollar Tree from a small, regional retailer to a world class, Fortune 150 Company across the United States and Canada. Our retail business model can operate successfully in tough times and good times, as we have demonstrated under Bob’s leadership as CEO.”

Philbin added that he was proud to follow in Sasser’s footsteps.

“I am honored to lead 180,000 dedicated associates that have made the Dollar Tree and Family Dollar brands the trusted solution for so many of our customers’ needs,” he said. “They live our vision to serve and delight our customers every day. We have a strong, dedicated and capable leadership team in place to grow and improve both banners for many years. We look forward to driving our performance, delivering value to long-term shareholders and providing opportunity for our many associates across the U.S. and Canadian markets.”