This paper explores the profound implications of quantum computing on cryptography, focusing on the vulnerabilities it introduces to classical encryption methods such as RSA and ECC, and the emergence of quantum-resistant algorithms. It reviews the core principles of quantum mechanics, including superposition and entanglement, which underpin quantum computing and cryptography. The paper examines quantum encryption algorithms, particularly Quantum Key Distribution (QKD) protocols and post-quantum cryptographic methods, highlighting their potential to secure communications in the quantum era. The analysis emphasizes the urgent need for developing robust quantum-resistant cryptographic solutions to safeguard sensitive information against the imminent threats posed by advancing quantum technologies. The paper also discusses the advantages and challenges of quantum cryptography, including unconditional security, future-proof security, and tamper detection. It reviews various QKD protocols, such as BB84, E91, SARG04, Twin-Field QKD, Coherent-One-Way QKD, and Continuous-Variable QKD, and explores fully quantum encryption methods like the quantum one-time pad and quantum homomorphic encryption. The paper addresses security considerations in quantum encryption, future directions, and challenges, including quantum hardware development, standardization, and regulatory and ethical considerations. Finally, it discusses the applications of quantum cryptography in secure communications, research and development, commercial applications, IoT security, smart grids, financial transactions, government and military, aerospace and satellite communications, telecommunications, and healthcare data. The conclusion highlights the importance of integrating quantum cryptography with quantum computing, advancing QKD protocols, and addressing practical challenges for real-world implementation and standardization.This paper explores the profound implications of quantum computing on cryptography, focusing on the vulnerabilities it introduces to classical encryption methods such as RSA and ECC, and the emergence of quantum-resistant algorithms. It reviews the core principles of quantum mechanics, including superposition and entanglement, which underpin quantum computing and cryptography. The paper examines quantum encryption algorithms, particularly Quantum Key Distribution (QKD) protocols and post-quantum cryptographic methods, highlighting their potential to secure communications in the quantum era. The analysis emphasizes the urgent need for developing robust quantum-resistant cryptographic solutions to safeguard sensitive information against the imminent threats posed by advancing quantum technologies. The paper also discusses the advantages and challenges of quantum cryptography, including unconditional security, future-proof security, and tamper detection. It reviews various QKD protocols, such as BB84, E91, SARG04, Twin-Field QKD, Coherent-One-Way QKD, and Continuous-Variable QKD, and explores fully quantum encryption methods like the quantum one-time pad and quantum homomorphic encryption. The paper addresses security considerations in quantum encryption, future directions, and challenges, including quantum hardware development, standardization, and regulatory and ethical considerations. Finally, it discusses the applications of quantum cryptography in secure communications, research and development, commercial applications, IoT security, smart grids, financial transactions, government and military, aerospace and satellite communications, telecommunications, and healthcare data. The conclusion highlights the importance of integrating quantum cryptography with quantum computing, advancing QKD protocols, and addressing practical challenges for real-world implementation and standardization.