Harvard is in The Associated Press' Top 25 for the first time.
The Crimson are 8-0, with a victory over then-ranked Florida State. They are one of four teams to join the men's college basketball rankings, but Georgetown, Creighton and Illinois have all been regulars compared to No. 25 Harvard.
Kentucky (8-0) beat North Carolina on Saturday and holds the No. 1 spot for a second straight week. The Wildcats received 47 first-place votes Monday from the 65-member national media panel.
Ohio State (8-0) had the other 18 first-place votes to remain second. Syracuse, which beat Florida last week, moved up a spot to third. North Carolina, Louisville and Baylor are fourth through sixth, each advancing a place.
Harvard is the first Ivy League school to be ranked since Princeton cracked the top 10 late in the 1997-98 season. The only other Ivy League school to be ranked since 1970 was Penn, which was last in the poll in January 1995. Brown is now the only Ivy League school not to make the poll.
The Crimson's stay among the basketball elite might not last long — they play at No. 9 Connecticut on Thursday.
Duke, which lost to Ohio State, dropped from third to seventh and was followed by Xavier, Connecticut and Missouri.
Georgetown (7-1) moved into the rankings at No. 18, one place ahead of Creighton (7-0). Illinois (8-0) is 24th, one place in front of Harvard. Georgetown and Illinois were both ranked last season. Creighton's last appearance in the poll was the first two weeks of 2006-07.
Marquette was 11th followed by Florida, Kansas, Wisconsin, Pittsburgh, Alabama, Mississippi State, Georgetown, Creighton and Michigan. The last five ranked teams were Memphis, Texas A&M, Gonzaga, Illinois and Harvard.
UNLV and Saint Louis both fell from the rankings after a one-week appearance while Vanderbilt and California also dropped out.
UNLV (8-1), which beat then-No. 1 North Carolina, fell out from 18th after losing at Wichita State on Sunday. Saint Louis (7-1) dropped out after losing at Loyola Marymount.
Vanderbilt (5-3) was No. 7 in the preseason Top 25 but has been playing without center Festus Ezeli, whose right knee injury should keep him about two more weeks. The Commodores lost to Xavier and Louisville, both in overtime. California (6-2) was 24th before losing to San Diego State on Sunday.