Eintracht Frankfurt clinched a place in the Europa League final and ended West Ham's dream run as Rafael Borre netted in a 1-0 win over the 10-man visitors.
David Moyes' team had Aaron Cresswell sent off for preventing a clear goalscoring chance early on, before Borre put Oliver Glasner's hosts in front with a neat finish after 26 minutes.
West Ham struggled to create clear-cut chances despite putting in a spirited performance, as their strong European run came to a disappointing end with a 3-1 aggregate defeat.
Despite sitting 11th in the Bundesliga, Frankfurt could end the campaign by securing a major European trophy and a spot in next season's Champions League by winning the May 18 final in Seville.
After a scrappy start, West Ham were dealt a huge blow when Cresswell hauled Jens Hauge down on the edge of the area 18 minutes in, with the VAR advising referee Jesus Manzano to send off the left-back before Filip Kostic drove the resulting free-kick wide.
The hosts needed less than 10 minutes to make their numerical advantage count, as Borre swept a side-footed finish into the bottom-left corner after meeting Ansgar Knauff's cut-back.
The Hammers struggled to assert themselves in a boisterous atmosphere, but almost found a surprise equaliser when Evan Ndicka cleared off the line after Jarrod Bowen's free-kick struck Kurt Zouma at the back post.
Borre hit a left-footed volley into Alphonse Areola's arms immediately after the break, before Craig Dawson headed Michail Antonio's cross straight at Kevin Trapp after an hour.
Moyes was sent off for a touchline outburst as West Ham's European dream slipped away, before Tomas Soucek missed a glaring headed chance in the final minute as the hosts cruised into the final.
What does it mean? Frankfurt build on first-leg triumph for historic semi-final win
Frankfurt's victory saw them reach their first European final since the 1980 UEFA Cup, when they beat Borussia Monchengladbach on away goals after a two-legged 3-3 aggregate draw.
With the win, Glasner's men have also become the first German team to reach finals in both the Europa League and UEFA Cup.
Hammers left deflated after Cresswell red
West Ham's hopes of reaching their first major European final since the 1975-76 Cup Winners' Cup were dealt a monumental blow when Cresswell became the first English player to ever receive two red cards in a single season in a European competition.
Cresswell was also sent off against Lyon in the last round, and is the first English player to be shown red in a European semi-final since Chelsea's John Terry in 2012 (against Barcelona in the Champions League).
Borre continues continental run
As well as recording seven goals and four assists in the Bundesliga this season, Borre has been in inspired form in Frankfurt's Europa League knockout games.
His composed finish means he has either scored (two) or assisted (one) three of Frankfurt's last five Europa League goals.
What's next?
Frankfurt host Borussia Monchengladbach in the Bundesliga on Sunday, while West Ham must turn their attentions back to securing European football for next season when they travel to Norwich City in the Premier League on the same day.