The Irish side secured their place with a victory over Faroese outfit KI Klaksvik in the final qualifying round, and will now face the Gunners home and away in Group B.
The other two sides in the group are Austrian club Rapid Vienna and Molde from Norway.
The draw for the Europa League group stages have taken place.
We will face Arsenal, Rapid Vienna and Molde in Group B.#CmonTheTown #UEL pic.twitter.com/mJpCbKp39X— Dundalk FC (@DundalkFC) October 2, 2020
Celtic and Rangers were drawn against sides with great European pedigree, with the Hoops facing seven-times European Cup winners AC Milan and the Light Blues taking on two-time champions of Europe Benfica from Portugal.
Celtic, who were losing UEFA Cup finalists in 2003, will also face Czech side Sparta Prague and French club Lille in Group H.
Neil Lennon’s side dropped into the Europa League qualifiers after being knocked out of the 2020-21 Champions League by Ferencvaros of Hungary.
Rangers will face Standard Liege of Belgium and Polish side Lech Poznan in Group D, in addition to the glamour trip to Lisbon.
Tottenham, UEFA Cup winners in 1972 and 1984, have been drawn against Bulgarian side Ludogorets, LASK of Austria and Royal Antwerp from Belgium in Group J.
Jose Mourinho’s men secured their place in the group phase after a 7-2 victory over Israeli side Maccabi Haifa on Thursday night.
The final Premier League representatives, Leicester, will take on Braga of Portugal, Greek side AEK Athens and Zorya Luhansk from Ukraine in Group G.
Prior to the draw, Inter Milan striker Romelu Lukaku was named the best player in the 2019-20 Europa League.
The Belgian forward’s goals were crucial to Inter reaching the final, but his own goal proved decisive in a thrilling final defeat to Sevilla in Cologne in August.