The Saints smashed their transfer record with a bid of £12m to bring Ramirez from Bologna last year, but the Uruguay international struggled to find his feet in the Premier League.
Borussia Dortmund and Atletico Madrid are both believed to be interested in Ramirez if he wants to leave England, but Pochettino has no intention to sell the midfielder.
"He's happy with us and we are counting on him for next season," he said.
"It's normal that a lot of clubs are interested in his quality, but we don't listen to transfer rumours. We are planning for next season with him on board."
Southampton have made just one signing, with centre-back Dejan Lovren joining from Lyon in an £8.5m deal, and Pochettino admits this arrival ended his interest in Cagliari centre-back Davide Astori.
"Lots of names have been linked with Southampton, perhaps too many," he said. "Some of them have been invented, others not.
"We were after Astori, for example, but in the end we went for Lovren instead. He's a great player."
Pochettino dismissed claims of a possible move for Astori's Cagliari team-mate Radja Nainggolan and also ruled out an approach for Roma's Pablo Osvaldo.
Reports suggested the striker rejected a £17m move to Saints, but the Argentinian insisted he did not make an offer for Osvaldo, who played under him during his spell as a manager in Spain.
"Osvaldo is a great player," Pochettino said. "I worked with him at Espanyol so I know what he can do.
"We are aware of his situation at Roma, but we haven't made an offer.
"We have a clear idea of what our targets should be but the market is moving very slowly at the moment. We are working prudently to reinforce the squad."