The unbeaten Lady Wave, 21-0 overall and 5-0 in the division, knocked off their DeSoto County visitors in three straight games: 25-11, 25-12, 25-7.
"The ranking was a surprise," Tupelo first-year coach Laurie Bishop said. "We're thrilled and honored to be nationally recognized.
"Everybody has taken on their role. We're all working together."
Olive Branch (4-13, 1-4), only got as close as 7-5 early in the second game.
Kelsey Burnis, a junior outside hitter who paced the Lady Wave with 10 kills and 13 service aces, believes the team still has room for improvement.
"If I had to rate us 1 through 10, I'd say we're a 9," said Burnis, who played last season in Wake Forest, N.C. "We can work harder and be a lot better.
"I'm really excited about the ranking and our record."
In Tupelo's 25-7 win in the third game, Burnis used her powerful jump serve to record eight of her aces.
Farmer kills it
Hannah Farmer, a 6-foot-3 middle blocker, recorded two of her match-high 12 kills in the final game. She also had an ace. Camille Walker added seven kills and Sarah Farmer six.
Sarah Farmer, a senior, has recovered from an ankle injury she received in a match late last month. Her first match back was last week's division win over Southaven.
Brena Medcalf, a 5-7 senior setter, led the way with a whopping 29 assists. She also had five service aces.
"I keep encouraging (Medcalf) that we don't have all the those kills without her," Bishop said.
Tupelo is off the remainder of the week before returning to action Sept. 13 at Caledonia. The Lady Wave returns to division action Sept. 15 with a road match against Southaven.
"Everybody is on their game and doing what it takes to win points," Bishop said. "That's what it will take for us to continue winning."