Today's draw, held in Nyon, Switzerland, will start at 11.45 CET, with ten teams allocated to the Champions Route and ten to the League Route.
There are five qualifier games in the 'Champions Route' - Celtic being one of the teams - that came through the third qualifying round.
Five other qualifier games are in the 'League Side' of the draw, where the likes of Arsenal, AC Milan, FC Schalke, Real Sociedad and FC Paços de Ferreira have all been registered.
Five in each section are seeded according to the club rankings established at the start of the season, and will be drawn against the other five. Balls containing the seeded teams will be placed in one bowl, with balls for the unseeded clubs positioned in another.
The ten winners of the play-off round ties join 22 automatic entrants in the group stage draw in Monaco on 29 August.
Seeded: Arsenal FC, Olympique Lyonnais, AC Milan, FC Schalke 04, FC Zenit St Petersburg
Unseeded: PSV Eindhoven, FC Metalist Kharkiv, Fenerbahçe SK, Real Sociedad de Fútbol, FC Paços de Ferreira
Seeded: FC Basel 1893, Celtic FC, FC Steaua Bucureşti, FC Viktoria Plzeň, GNK Dinamo Zagreb
Unseeded: FK Austria Wien, Legia Warszawa, NK Maribor, PFC Ludogorets Razgrad, FC Shakhter Karagandy