Elizabeth T Kennan, 39, an associate professor of history at Catholic University here, has been named president of Mount Holyoke College in South Hadley, Mass., it was announced last night.

Kennan, director of Medieval and Byzantine Studies at Catholic and director of its Program in early Christian Humanism, will succeed David B. Truman, who will retire in June.

Truman announced the appointment last night at ceremonies marking the opening of the second semester of the 141-year-old college for women. Mount Holyoke has 1,850 students.

"Elizabeth Kennan's professional credentials are impeccable, and her personal qualities will command the loyalty and enthusiasm of the entire Mount Holyoke family," Truman said in making the announcement.

Kennan is married to Martin L. Budd, a lawyer who is director of the Special Study of the Options Market at the Security and Exchange Commission. They live at 4630 Broad Branch Rd. N.W.

In a formal statement last night, Kennan affirmed her commitment to the principle of women's colleges.

"Only here can women develop the strength and resilience to enable them to deal with the discrimination which still remains and with the cross-cutting resposiblities of family life which will always remain," she said.

A 1960 graduate of Mount Holyoke, Kennan will become president July 1. She was the unanimous choice of a 13-member search committee that considered more than 450 candidates.