Sunak on Tuesday took over as Britain's new prime minister after being appointed by King Charles.
"My warmest congratulations to Rishi Sunak on becoming the UK’s prime minister," Poland's President Andrzej Duda said in a Twitter post.
"I am looking forward to our meeting and co-operation and wish you success in your endeavours," he added.
Poland, UK 'standing together against Russian invasion of Ukraine'
Duda also tweeted that Poland and Britain "are steadfast allies and are standing together against the Russian invasion of Ukraine."
'I wish you every success': Polish PM
Polish Prime Minister Mateusz Morawiecki tweeted: "Congratulations to Rishi Sunak on becoming Great Britain’s PM. I wish you every success and count on a further strengthening of our partnership."
'Our country is facing a profound economic crisis': Sunak
Sunak, who is the UK's first prime minister of Indian origin, replaces Liz Truss, the shortest-serving leader in British history.
A day earlier, he won the race to lead the country's governing Conservative Party.
In his first speech as prime minister, Sunak on Tuesday acknowledged the mistakes of his predecessor, while vowing to fix the economy and deliver on the promises of his Conservative Party, the Reuters news agency reported.
"Right now, our country is facing a profound economic crisis," Sunak said.
"The aftermath of COVID still lingers. Putin's war in Ukraine has destabilised energy markets and supply chains the world over," he added.
He vowed to place "economic stability and confidence" at the heart of his government's agenda.
"This will mean difficult decisions to come," he said.
He promised to "work day in, and day out to deliver" for the British people.
Rishi Sunak on Tuesday promised to "work day in, and day out to deliver" for the British people as the UK's new prime minister. EPA/TOLGA AKMEN
Sunak graduated from Oxford University and then studied at Stanford University in the United States, where he met his wife Akshata Murthy, whose father is Indian billionaire N. R. Narayana Murthy, founder of outsourcing giant Infosys, according to Reuters.
Sunak’s grandparents were born in India and his parents emigrated to Britain from East Africa in the 1960s, US broadcaster CNN has reported.
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Source: PAP, Reuters, CNN