However, he stopped short of backing the Yorkshire-wide devolution deal put to him by the region’s leaders earlier this week.
In a statement, Mr Johnson said: “I want to wish everyone a very happy Yorkshire Day! What a fantastic and varied county yours is – from its sweeping countryside, to its buzzing cities packed with culture and the famous produce sold around the world.
“It’s no surprise that millions of visitors from around the world flock to Yorkshire every year and I’m wholeheartedly looking forward to visiting again soon.
“Local leaders wrote to me recently about plans for giving more powers to representatives here. I want everyone in Yorkshire to know that I strongly believe our towns, cities and counties must have greater self-governance.
The Prime Minister added: “I know there’s wide support for more devolution here and we must now move forward with an approach that’s practical, while giving communities a much greater say over transport, housing, public services and infrastructure that will drive growth and see long-lasting benefits for families and businesses in this great region.”
Mr Johnson’s words came amid a fresh push by some of the county’s most influential figures to win backing for the One Yorkshire deal, which was rejected under Theresa May’s government in favour of smaller, city-focussed agreements.
A new One Yorkshire Committee - co-chaired by Keighley MP John Grogan and Lord Kirkhope of Harrogate - will champion the initiative, which would see the election of a Mayor for Yorkshire supported by a cabinet of council leaders by 2022.
As part of the campaign, the Archbishop of York John Sentamu will lead a delegation from Yorkshire to London on 8 October to discuss the plan with Westminster’s political leaders.
Archbishop Sentamu said: “Talk of One Yorkshire is a conversation that needs to happen – for the benefit of all the people of God’s own county! Many Peoples, Boroughs, Councils and Counties, but One Yorkshire working together towards a strong, prosperous, diverse, creative and open Yorkshire.
“A place of shared opportunity. I simply want to act as convenor, to make sure the necessary dialogue happens, for the sake of the common good. Let us listen, and let us speak.”
In a letter to Mr Johnson sent earlier this week, Sheffield City Region Mayor Dan Jarvis and a host of council leaders called on the Prime Minister to back an ambitious plan for devolution that would unlock Yorkshire’s potential after Brexit.
They wrote: “Devolution in Yorkshire is critical to deliver our shared objectives, which cross political divides and are about growth in a post-Brexit world.
“We hope that you will consider our proposal favourably, and we would of course welcome the opportunity to discuss these matters with you.
“It would send the clearest signal of intent to the people of Yorkshire to receive confirmation of your support for our proposal on or before Yorkshire day on 1 August. Together we can unlock the potential for Yorkshire!”