The 40-year-old American player avoided the big names in Friday's draw and will get the chance to ease into the tournament against world No. 113 Tan as she targets an eighth singles title at the All England Club.
Williams, notionally ranked down at 1,204 and therefore a wild card next week, has not played a singles match since retiring injured and in tears in the first round a year ago against Aliaksandra Sasnovich.
Second-seeded Rafael Nadal, who is halfway to a calendar-year Grand Slam, plays world No. 42 Francisco Cerundolo in the first round, and Spanish compatriot Carlos Alcaraz takes on Germany's Jan-Lennard Struff.
Raducanu, 19, has struggled since her incredible run in New York and has been dealing with an injury in the build-up.
On the men's side, standout first-round matches include three-time Grand Slam champion Stan Wawrinka against rising Italian Jannik Sinner, and Australian maverick Nick Kyrgios takes on British hopeful Paul Jubb.
Looking further into the draw, Djokovic is on course to face fifth-seeded Alcaraz in the quarterfinals, and last year's runner-up Matteo Berrettini, who opens against Chile's Cristian Garin, could face Stefanos Tsitsipas.
Nadal's seeded quarterfinal opponent is Canada's Felix Auger-Aliassime, whom he beat on the way to the French Open title.
Swiatek's projected quarterfinal opponent is American Jessica Pegula.