Ruben struck five minutes before half-time and although the visitors rallied late on they could not force an equaliser as Levante picked up their first win since beating Valladolid.
Victory sees the hosts leapfrog today's opponents to go 10th in the Primera Division.
Sevilla had the first real effort, Jesus Navas shooting wide but it was the hosts who were first to force the opposition goalkeeper into action.
Herrero Michel's corner from the right was met by Vicente Iborra whose header was parried by Sevilla goalkeeper Antonio Beto.
Juanfran Garcia headed Michel's free-kick over the bar but there was nothing in the way of clear-cut chances until the hosts took the lead six minutes before the break.
Beto was left with no chance as Garcia Ruben fired a 25-yard shot into the bottom right-hand corner of the goal.
Robert Acquafresca then had his shot comfortably held by Beto as the first half ended with Sevilla having offered nothing as an attacking force.
Loukas Vyntra headed Michel's corner over for Levante as the second half resumed in much the same manner as the first had ended.
Sevilla finally mustered an attempt on goal as Alvaro Negredo fired over from distance.
It seemed to spark the visitors into life with Navas forcing home keeper Gustavo Munua into saving his close-range shot with his feet.
It was then Beto's turn to keep his side just one goal down as he pushed away Acquafresca's shot from the right and David Navarro headed over as the match enjoyed a lively period.
Ivan Rakitic fired in a 25-yard shot from the left which was parried by Munua but again Sevilla were grateful to Beto who produced a fantastic reaction save from Garcia Ruben's shot from the centre of the area.
Negredo pushed a shot wide from the six-yard box as time wound down with Papakouli Diop firing past the post for the home team.
As the match moved into injury-time, Negredo was on the brink of an equaliser but he saw Munua managed to repel his right-footed shot.
Federico Fazio headed over from Sevilla but it was too little too late as Levante held out for all three points.