Russia's first regiment of Avangard hypersonic missiles has been put into service, the defence ministry says.
The location was not given, although officials had earlier indicated they would be deployed in the Urals.
President Vladimir Putin has said the nuclear-capable missiles can travel more than 20 times the speed of sound and put Russia ahead of other nations.
They have a "glide system" that affords great manoeuvrability and could make them impossible to defend against.
Defence Minister Sergei Shoigu confirmed the "Avangard hypersonic glide vehicle entered service at 10:00 Moscow time on 27 December", calling it a "landmark event".
Mr Putin said on Tuesday the Avangard system could penetrate current and future missile defence systems, adding: "Not a single country possesses hypersonic weapons, let alone continental-range hypersonic weapons."
The West and other nations were "playing catch-up with us", he said. Mr Putin unveiled the Avangard and other weapons systems in his annual state-of-the-nation address in March 2018, likening it to a "meteorite" and a "fireball".
In December 2018, the weapon hit a practice target 6,000km (3,700 miles) away in a test launch at Dombarovskiy missile base in the southern Ural Mountains.
"The Avangard is invulnerable to intercept by any existing and prospective missile defence means of the potential adversary," Mr Putin said after the test.