Original text
ॐ नमो भगवते वासुदेवाय
Transliteration
Om Namo Bhagavate Vasudevaya
What the words mean
Om, the primordial sound; namo, "salutations"; Bhagavate, "to the Lord"; Vāsudevāya, "to Vasudeva." The Vishnu Purana explains Bhagavan as the one who possesses the six bhagas in full — sovereignty, righteousness, glory, prosperity, knowledge and detachment. Vāsudeva means Krishna as the son of Vasudeva, and is also read as "the Lord who dwells in all beings and in whom all beings dwell." So the mantra is a salutation to God as both the personal Krishna and the all-pervading Vishnu.
The twelve-syllable mantra
It has exactly twelve syllables — om, na, mo, bha, ga, va, te, vā, su, de, vā, ya — which is why it is called the Dvadashakshari. Vaishnava tradition sometimes connects the twelve syllables with the twelve months and with the twelve names of Vishnu recited in daily worship.
Where it comes from
Two moments in the Shrimad Bhagavatam make this mantra especially beloved. The Bhagavatam itself begins with it: its very first verse (1.1.1) opens "oṁ namo bhagavate vāsudevāya." And in the fourth canto (4.8.54), the sage Narada gives this mantra to the five-year-old Dhruva, hurt by his stepmother's words, and tells him to meditate on it in the forest of Madhuvan. Through this mantra Dhruva receives the vision of Vishnu himself — and becomes the pole star, the symbol of unwavering devotion.
How and when to chant it
It is traditionally chanted as japa on a tulsi mala of 108 beads, and is widely practised by Vaishnavas of every tradition. Thursdays, Ekadashi, Janmashtami and the month of Kartik are especially favoured. Pair it with the Vishnu Gayatri Mantra, the Vishnu Chalisa or Krishna Chalisa, and close with the aarti Om Jai Jagdish Hare. See also Ekadashi Vrat and Thursday Vishnu Bhakti.