Twofish
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A symmetric block cipher with a 128-bit block and keys of 128, 192 or 256 bits, one of the five finalists in the competition that selected AES. It was not chosen and is not a NIST-approved algorithm; PCI DSS names neither it nor any other algorithm.
Applies to. PCI DSS v4.0.1 names no algorithm, Twofish included; it asks for strong cryptography and leaves the choice to the entity. Whether Twofish qualifies turns on the Council's definition, which asks for an industry-tested and accepted algorithm with at least 112 bits of effective key strength and points to NIST SP 800-57: Twofish's key lengths clear the bit threshold, but it is not among the algorithms NIST approves, so an entity choosing it should expect to justify the choice to its assessor, list it in any cryptographic architecture document and track its continued viability in the annual cipher suite review under Requirement 12. Being an AES finalist is not itself a PCI DSS credential.