WATERVILLE — Robert E. Diamond Jr., a leader in international finance, will be the speaker May 25 at Colby College’s 187th commencement ceremonies.

A 1973 Colby alumnus who majored in economics, Diamond is president of the London-based financial services firm, Barclays PLC.

He also is chief executive of investment banking and investment management, comprising Barclays Capital, Barclays Global Investors and Barclays Wealth. He is the architect of strategies that have produced record performances for Barclays across those divisions.

Diamond will receive an honorary degree, as will art historian Gabriella De Ferrari, who has served as curator and director of the Institute of Contemporary Art in Boston and curator of Harvard’s Busch-Reisinger Museum; Amory Lewis, co-founder, chairman and chief scientist of the Rocky Mountain Institute; David Simon, author, journalist and television writer-producer who began his career as a reporter for the Baltimore Sun; and Sunita Williams, a woman astronaut who has spent 195 days in space. A naval aviator, Williams was selected for the astronaut program in 1998. Her four space walks totaling 29 hours and 17 minutes established the world record for women.