Mangalam Bhagwan Vishnu Mantra is a very devine Mantra of Lord Vishnu which is chanted for the auspiciousness in most of the Hindu rituals.
मङ्गलम् भगवान विष्णुः, मङ्गलम् गरुडध्वजः।
मङ्गलम् पुण्डरी काक्षः, मङ्गलाय तनो हरिः॥
Mangalam Bhagwan Vishnuh, Mangalam Garudadhwajah।
Mangalam Pundari Kakshah, Mangalaya Tano Harih॥
All auspiciousness to Lord Vishnu, all auspiciousness to one who has Garuda as His flag. All auspiciousness to One who has eyes like the lotus flowers, and auspiciousness to Hari.