Jeremy Corbyn says he is "very confident" there is support in Wales for his bid to retain the Labour leadership.
Mr Corbyn, who is being challenged by Pontypridd MP Owen Smith, visited Merthyr Tydfil and will go to Swansea on Friday.
They took part in the first hustings of the leadership contest in Cardiff on Thursday night.
Mr Corbyn said no community in Wales would be "left behind".
He spoke to hundreds of supporters at a rally in Merthyr Tydfil's Penderyn Square, the scene of the start of the 1831 Merthyr Rising.
"We're reaching out to every community in every part of this country," he told the crowd.
"Yes, in order to take part in this election, yes, in order to strengthen our party, but also to reach out to those who have become disillusioned with politics because they don't see a political solution to their problems", Mr Corbyn said.
As the Labour leader left the event he was followed by a large group of supporters, some of whom asked for "selfies" or tried to speak to the leader.
Ahead of the visit, Mr Corbyn told BBC Wales he was "very confident" in the support for his leadership in the south Wales valleys.
"We had the event last night in Cardiff. We've got the event today in Merthyr and were going on to Swansea this evening. We're doing a lot of campaigning all over the UK.
"No-one and no community will ever be left behind by Labour," he said.
The Labour leader Mr Corbyn claimed Labour had gained seats at the last assembly election, despite the party's overall number of Senedd seats having fallen from 30 to 29.
"The assembly election results, we gained some seats as well as losing one," he said. "We've made a lot of progress there."
In fact, Labour won no extra seats at the May poll, and lost Rhondda to Plaid Cymru.
Meanwhile, Mr Smith has won his first trade union endorsements from Community and the Musicians' Union.
Mr Corbyn is being supported by Aslef, Communication Workers Union, the Fire Brigades Union and the Union of Construction, Allied Trades and Technicians.
During Thursday's hustings, Mr Corbyn vowed to fight to keep Port Talbot Steelworks open and also to invest in transport projects.
Mr Smith said he would invest an extra £1bn a year in resource funding, saying the Welsh Government could increase spending on the NHS by 4% every year in the next parliament.
Party members, affiliated trade union supporters and so-called registered supporters are able to vote in the election.
The result of the poll will be announced on 24 September.
One of Mr Corbyn's Merthyr Tydfil-based supporters is Margaret Davies, mayor of the county council and Labour councillor for Cyfarthfa ward.
Speaking in a personal capacity she said Jeremy Corbyn "has spent his life by" his policies. "I trust Mr Corbyn to implement those policies," she said.
Brendan Toomey, Merthyr Tydfil Labour council leader, is backing Owen Smith. He said he was supporting the challenger "because he's got a coherent plan for government".
On Thursday, Mr Smith told BBC Radio Wales he feared the Labour Party could not close the gap on the Conservatives.
"Most people in the country don't think the Labour Party is going places, most people think Labour has lost credibility in recent years and lost further credibility in recent months," he said.
On the same day Mr Corbyn set out 10 pledges "to rebuild and transform Britain", promising to invest £500 billion in infrastructure, manufacturing and industry.
"For too long, too many communities in Britain have been neglected, too many people's potential has been left untapped and their talents undeveloped," he said.