Speaking ahead of a meeting of the Ukraine defence contact group at Ramstein air base in Germany, he also told reporters that, once the war in Ukraine ends, Kyiv must have "the deterrence to prevent new attacks".
He said that the main focus is now to ensure the country prevails against Russia.
It comes after Mr Stoltenberg yesterday pledged continued support for the country during his first visit to Kyiv since Russia's invasion just over a year ago.
"Let me be clear, Ukraine's rightful place is in the Euro-Atlantic family," he told a news conference.
"Ukraine's rightful place is in NATO."
Meanwhile, Kremlin spokesman Dmitry Peskov said on Thursday that preventing Ukraine from joining NATO remains one of the goals of what Moscow calls its "special military operation."
He said that Ukraine's accession would pose a "serious, significant threat to our country, to our country's security".
President Volodymyr Zelenskyy said earlier this year that he was grateful for an invitation into the alliance, but said his country needs a roadmap for becoming a member.
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In May, Finland joined the alliance, setting aside years of military nonalignment, in order to seek protection under the organisation's security umbrella after Russia's invasion of Ukraine.
The country's accession dealt a major political blow to Russian President Vladimir Putin as it doubled the size of NATO's border with the nation.
Neighbouring Sweden is also expected to join, but so far Turkey has blocked its approval due to "security concerns".
NATO allies have trained tens of thousands of Ukrainian troops and provided €65bn (£57bn) of military aid alone.
On Friday, the Canadian government announced a further $28.9m (£23.3m) in military aid that will include 40 sniper rifles, 16 radio sets and a donation to a NATO fund to help Kyiv in the war.
A day earlier, both Denmark and the Netherlands said they plan to provide Ukraine with at least another 14 refurbished Leopard 2 battle tanks by early 2024 - tanks that the country pleaded Western nations for, in order to give its forces the firepower they need to retake occupied territory.