Canto 3 -
Araṇya-kāṇḍa
Chapter 47: Rāvaṇa Reveals his Identity to Sītā
Text 3.47.3

दुहिता जनकस्याहं मैथिलस्य महात्मनः।
सीता नाम्नास्मि भद्रं ते रामभार्या द्विजोत्तम॥

duhitā janakasyāhaṁ maithilasya mahātmanaḥ
sītā nāmnāsmi bhadraṁ te rāma-bhāryā dvijottama

duhitā = the daughter; janakasya = of Janaka; aham = I; maithilasya = King of Mithilā; mahā-ātmanaḥ = the greatly strong; sītā = Sītā; nāmnā = named; asmi = am; bhadram = auspiciousness; te = unto you; rāma-bhāryā = and Śrī Rāma’s wife; dvija-uttama = O best of the twice-born.

O best of the twice-born, auspiciousness unto you! Named Sītā, I am the daughter of Janaka, the greatly strong King of Mithilā, and Śrī Rāma’s wife.

Here is the answer to Rāvaṇa’s question to her, “Who are you?” The answer to his question, “Whom do you belong to?” is “I am Śrī Rāma’s wife.”

She responds to his other questions, such as from which place she had come, in the following verse.