The first leg will take place at El Madrigal in Spain on Thursday 28 April before the tie will be settled at Anfield a week later on Thursday 5 May.
Liverpool, who have won the competition three times before in its previous guise as the Uefa Cup, earned their place in the final four after a dramatic 5-4 aggregate victory over Borussia Dortmund in the quarter-final.
Villarreal are the only side left in the competition not to have won it before, yet they will be no light touch - only the powerhouses of Atletico Madrid, Real Madrid and Barcelona have more points in this year's La Liga.
Should Jurgen Klopp guide his side to a first European final in nine years, they will be considered the home team at the final in Basel on Wednesday 18 May. There they will meet either Shakhtar or Sevilla.
Thursday 28 April:
- Shakhtar Donetsk v Sevilla
- Villarreal v Liverpool
Thursday 5 May:
- Sevilla v Shakhtar Donetsk
- Liverpool v Villarreal