French striker Jeremie Aliadiere has joined West Ham on loan from Arsenal.
The 22-year-old joined Celtic in July on a year-long loan but has decided to move back to the Premiership, with the Hammers taking over the deal.
Aliadiere made only two appearances for the Glasgow side, both as a substitute against Artmedia Bratislava in the Champions League qualifying round.
"I am very disappointed this has not worked out the way I thought it would," the Frenchman said.
A Celtic spokesman said: "Unfortunately, things didn't work out in a football sense for Jeremie and he wanted to return to England."
Even after a long-term injury to Chris Sutton, Aliadiere found himself behind John Hartson, new signing Maciej Zurawski, and in-form youngsters Shaun Maloney and Craig Beattie.
He had been particularly looking forward to Champions League football with Celtic, but the Glasgow club fell to Artmedia in the first qualifying hurdle.