Gareth Southgate’s men dominated from the off and Borussia Dortmund midfielder Bellingham capped an excellent all-round display when he headed home the opener on 35 minutes.
The Three Lions then made it three goals in eight minutes as Saka and Raheem Sterling struck to round-off a first half that was disrupted by a lengthy delay following a concussion to Iran keeper Alireza Beiranvand.
England continued to boss it following the interval and Saka grabbed his second of the match just past the hour with a jinking run and shot.
Iran had barely threatened but pulled one back moments later when Mehdi Taremi rifled a fine first-time shot beyond Jordan Pickford.
Substitute Marcus Rashford then made it five within 49 seconds of taking to the pitch before Jack Grealish tapped home a sixth to round-off a great day for Southgate and co.
Iran were awarded a dubious penalty kick via VAR deep into stoppage-time, which they converted, but it mattered little.
England will face the USA in the next group game on Friday while Iran take on Wales.
