The Bulldogs (29-2) become the fifth team this season to reach the top of the poll, which has had a different No. 1 in eight of the last nine weeks. Gonzaga claims 29 of the 31 first-place mentions and two others for second,
Indiana (25-4) had its third turn at No. 1 ended after two weeks.
Gonzaga joins a list that includes Indiana (three times), Duke (twice), Kansas and Louisville as claiming the No. 1 ranking for at least one week this season.
While the Hoosiers fall to No. 2, third-ranked Kansas (25-4) rises two spots in getting a first-place mention. Duke (25-4) drops one place to fourth and rapidly rising Georgetown (23-4) goes from eighth to No. 5 this week.
Louisville (24-6), which takes the other first-place vote, is sixth with Miami (Fla.) keeping the No. 7 spot. Michigan (24-5) is down four places to eighth while Florida is down to No. 9 and Kansas State (24-5) goes from 13th to 10th this week.
New Mexico (25-4) also improves three places, moving to 11th while Michigan State (22-7) is down two to No. 12 and Ohio State (21-7) is up two to 13th. Oklahoma State (22-6) and St. Louis (23-5), both moving up four, are 14th and 15th, respectively.
Syracuse (22-7) falls four rungs to No. 16 but Marquette improves five to 17th. Arizona (23-6) has the biggest drop of the week, going from 11th to No. 18. Virginia Commonwealth (23-6) jumps six places to 19th. Memphis (25-4) takes the No. 20 position.
Wisconsin (20-9) comes in 21st and Pittsburgh (23-7) re-enters the Top 25 at No. 22. St. Mary's (Calif.) (26-5) is again 23rd with Notre Dame (22-7) and Oregon (23-6), unranked a week ago, in the 24th and 25th places.
Butler, No. 10 on Feb. 11, and Akron drop from the rankings.
Indiana has two games this week against ranked opponents, playing Ohio State Tuesday and at Michigan Sunday. Also in the Big Ten, Wisconsin is at Michigan State Thursday
The Big East, in the waning days in its current configuration, has Syracuse at Georgetown and Notre Dame at Louisville Saturday. In the Big 12, also Saturday, Kansas State is at Oklahoma State.