Both have both been strongly linked with moves away from Anfield to Spain this summer.
"I do not think Alonso or Mascherano will go. It is clear that they both are under contract with long-term agreements. That is it," insisted Benitez.
"There has been a lot of things written, a lot of rumours, but both players are under contract and we have no more need to talk about things.
"They are both very good players and I will be very pleased to keep them. They both have very good contracts.
"We signed them both from different situations. Alonso was coming from Real Sociedad and nobody had really heard much of him outside of Spain, he did well and we renewed his contract because of that.
"Mascherano came from West Ham where he had not been doing well. We brought him here and gave him a good contract, so we are very pleased with them both and that Liverpool has been very good to them."