The sportswear brand will replace fans' favourites Adidas as kit manufacturer from next season. That means Umbro will take on the unenviable task of coming up with a fitting design for the Hammers' special commemorative kit for their final season at the Boleyn Ground.
If that wasn't hard enough, Umbro will then have to follow that up by producing a kit for the team to wear when playing for the first time at the club's new 54,000 capacity Olympic Stadium down the road in Stratford.
A good kit which appeals to fans is vital for any football club and can generate millions of pounds in vital extra revenue. A bad kit can hit club coffers severely.
So designers at Umbro are already under pressure following in the footsteps of Adidas who, with the exception of a rather garish purple and gold third strip effort this season, have produced some very popular shirts during the last three years with the Hammers.
But now we want to know what you consider to be the club's best all-time home kit.
The 80s was a good era for the club on the pitch as it was when the Hammers last won a major trophy and almost won the league title. But they also did it in style with a succession of hugely popular kits.
First up was this Adidas kit worn from 1980 through to 1983 and it was the last West Ham shirt not to have a sponsor emblazoned across the chest.
Sporting the old Adidas Trefoil logo, retro reproductions of the shirt are still a real favourite on the terraces today, 35 years on. It is being worn here by Ray Stewart in a League Cup third round replay against West Bromich Albion. The kit came in the summer after West Ham's last major trophy victory, 1-0 over Arsenal at Wembley and evokes fond memories for the Hammers faithful.
Next up is another Adidas kit, this time from 1986 - the season when West Ham should have won the title with the deadly duo of Frank McAvennie and Tony Cottee up front. The Hammers ended up in third place which remains the club's best top flight finish.
The current West Ham home kit, also made by Adidas, was inspired by that 'Boys of 86' shirt.
With a string of hugely popular kits, Adidas proved a hard act to follow. But Scoreline made a decent fist of it producing a kit which has actually got more popular as time has gone on, some fetching hundreds of pounds on internet auction sites like eBay.
Featuring a centralised badge and V-neck, the two tone shirt sported here by Liam Brady in a match against Spurs, was worn from 1987 through to 1989 and like many of the other popular kits over the years, had a white away strip of the same design.
During the 70s the best kit was arguably this Admiral shirt worn in different guises from the 1976 European Cup Winners Cup final defeat to Anderlecht through to the 1980 FA Cup final win over the Gunners. Worn here by Tommy Taylor.
Turning the clock back further to what was another golden era in West Ham's history shows that sometimes simplicity works best. This plain kit was actually designed by Umbro and was worn by the likes of the legendary Bobby Moore in the 60s as he led the club to their famous European Cup Winners Cup victory - albeit in a slightly modified version the final (below).
The kit also mirrored the style of another of Umbro's products at the time, the England shirt in which Moore, Martin Peters and Geoff Hurst were to lift the World Cup a year later.
The next kit takes us back another decade into the early 1950s.
This shirt, sported here by former Hammer Dave Sexton, was the first West Ham shirt to include the club's famous crest. Worn from 1950-53 it again was very simplistic and has proved popular as a retro remake for modern fans.
Of the modern era what is arguably the most popular shirt coincided with it being worn by one of the club's legendary players.
Paolo Di Canio and his teammates wore this stylishly simple Fila kit from 2001 through to 2003.
The Hammers had a side brimming with talent at the time and secured one of their best seasons in the Premier League era by finishing seventh under Glenn Roeder.
Some fans were not too keen on the tight fitting nature of the shirt, which also had a pretty snug roundneck, but like other shirts in the club's history it is actually beginning to become more popular now, nearly 15 seasons later.
Now we want to know what you think so take our poll below.
If you need some help remembering the club's kits over the years Historical Kits has charted every single one.