Liberal Democrat AM Aled Roberts.
He will take over from Meri Huws when her term as Welsh language commissioner ends in March 2019.
The role promotes the Welsh language and protects the rights of speakers to use it.
Mr Roberts said he has "no doubt of the scale of the challenge ahead". First Minister Carwyn Jones said he was ideal for the role.
The ex-North Wales AM, who was a member of the assembly between 2011 and 2016, said: "I have always been passionate about the Welsh language and have greatly enjoyed recently working with local authorities on their plans for Welsh medium education and assisting the Welsh Government with their ambitions for the future of Welsh in education.
"I have no doubt of the scale of the challenge ahead and I am committed to forging effective relationships across Wales and beyond to meet it head on."