Rakṣakatva (from rakṣaka = protector + tva = -ness/quality-of) is one of the essential divine attributes (svarūpa-nirūpaka-dharmas) of Śrīman Nārāyaṇa in Viśiṣṭādvaita Vedānta. It signifies that protection (rakṣā) is not merely an occasional act of Bhagavān but belongs to his very nature (svarūpa). Bhagavān is intrinsically and eternally the rakṣaka — the one who shields, preserves, and liberates.
The scriptural foundation is the famous pledge of Śrī Rāma to Vibhīṣaṇa's envoy: 'sakṛdeva prapannāya tavāsmi iti ca yācate / abhayaṃ sarvabhūtebhyo dadāmyetad vrataṃ mama' — 'To one who once surrenders and says 'I am yours,' I grant fearlessness from all beings — this is my vow.' This abhaya-vacana is understood as a carama-śloka of the Rāmāyaṇa, parallel to the carama-śloka of the Bhagavad Gītā (18.66: mā śucaḥ), and encapsulates Bhagavān's unconditional protective commitment.
In the theology of prapatti (surrender), the prapanna (one who has surrendered) relies entirely on Bhagavān's rakṣakatva as the guarantee that the act of surrender will not be in vain. The Āchārya teaches the disciple to recognise that Bhagavān's capability (śakti), willingness (icchā), and knowledge (jñāna) together constitute his rakṣakatva, and that the jīva need add nothing to it beyond the simple act of surrender. This contrasts with other upāyas (means) such as karma-yoga and jñāna-yoga, where the sādhaka's effort is itself part of the means.