Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 5: The City of Ayodhyā
Text 1.5.3

इक्ष्वाकूणामिदं तेषां राज्ञां वंशे महात्मनाम्।
महदुत्पन्नमाख्यानं रामायणमिति श्रुतम्॥

ikṣvākūṇām idaṁ teṣāṁ rājñāṁ vaṁśe mahātmanām
mahad utpannam ākhyānaṁ rāmāyaṇam iti śrutam

ikṣvākūṇām = from Ikṣvāku; idam = this; teṣām = greatly powerful; rājñām = kings; vaṁśe = about a descendant in the dynasty; mahā-ātmanām = greatly powerful; mahat = great; utpannam = has been composed [by the mercy of Lord Brahmā]; ākhyānam = historical narration; rāmāyaṇam = Rāmāyaṇa; iti = as; śrutam = famous. 

This great historical narration about a descendant in the dynasty of those greatly powerful kings from Ikṣvāku famous as Rāmāyaṇa has been composed [by the mercy of Lord Brahmā].

The Rāmāyaṇa appeared by the blessings of Lord Brahmā. Vaṁśe here means vaṁśye, “a descendant in the dynasty.” The sage Vālmīki humbly considers himself a mere instrument in bringing about its appearance. The hero of this book has the excellence of possessing great fortune—the fortune of ruling over the entire planet, noted in the first text of this chapter—and the excellence of being born amongst greatly noble persons.