Vishnusahasranama is the Sanskrit hymn which has the 1000 names of the Supreme Lord- Vishnu. This was rendered in the 135th chapter of the Anushasana Parva of the Mahabharata- Verses 14 to 120. This stotra was given to Yudishtira by the grandsire of the Kuru Dynasty – Bhishmacharya while he lay on the bed of arrows during the war of Kurukshetra. After the war, when Yudishtira went to meet Bhishmacharya, he asked him this question
kimekam daivatam loke kim vāpyekam parāyaṇam
stuvantaḥ kam kamarcantaḥ prāpnuyurmānavāḥ śubham
ko dharmaḥ sarva dharmāṇām bhavataḥ paramo mataḥ
kim japan mucyate jantuḥ janmasamsārabandhanāt
In this world Who is the one refuge for all? Who is the greatest Divinity in the world ? By eulogising whom can a person reach auspiciousness? By worshipping whom can a person reach auspiciousness? What is, in your opinion, the greatest Dharma among all the Dharmas? By chanting whose name, can a creature proceed beyond the bonds of samsāra?
Bhishmacharya then replied to this question by mentioning that to free oneself from all sorrows, one has to chant the Vishnu Sahasranma, i.e. the thousand names of the all pervading Supreme Lord. Lets understand each of these 1000 Names and relish the meaning of each name/Nama. There are 107 Shlokas which contain these 1000 names.