Pablo Fornals scored twice as a youthful Hammers side thumped FCSB 3-0 on Thursday.
The Hammers were in control from the first minute and dominated their final game in the Europa Conference League group stage.
It means the Irons have won six from six in Europe, a superb achievement that guarantees European football after Christmas.
The Spaniard scored the first goal of the game after 40 minutes, as he got on the end of a superb pass from Ben Johnson and finished stylishly.
Divin Mubama, making his debut for the Hammers, scored the second.
The 18-year-old reached Vlad Coufal’s cross and headed towards goal at the back post; it took a deflection and found its way into the back of the net; the teenager’s celebrations were superb, as he appeared genuinely disbelieving.
Fornals scored his second on 65 minutes, smashing home after Ollie Scarles’ cross was palmed away.
An excellent victory for the Irons, and with a team made up of kids.