He said on Twitter: "I'm delighted to say I've joined the Lib Dems."
Ex-Liberal Democrat leader Tim Farron said: "Fantastic news. Welcome Chuka!"
The former shadow business secretary quit Labour in February to join the new Independent group, which then became Change UK ahead of the European elections last month.
He then went independent after disappointing election results.
Now the Streatham MP has joined the Lib Dems in a huge boost for the party.
“The Liberal Democrats are not – they were arguing for a People's Vote and to remain in the EU from the very start”
Umunna said the Liberal Democrats are "at the forefront" of "a progressive and internationalist movement" in British politics.
He added: "Labour and the Tories are committed to facilitating Brexit, and Brexit makes ending austerity virtually impossible.
"The Liberal Democrats are not – they were arguing for a People's Vote and to remain in the EU from the very start.
"I am convinced the Liberal Democrats, as the spearhead of a broader progressive movement in civil society, offer the best chance to improve the lives of those I represent as well as countless other citizens across our country."
Lib Dem leader Sir Vince Cable also welcomed him to the party.
He said: "Chuka and I have worked together effectively for many months, campaigningRead More – Source