In distributed systems, "blockchain consensus" refers to the mechanism used to achieve agreement among nodes on the validity of transactions and data blocks. Consensus algorithms, such as Proof of Work or Proof of Stake, ensure that every transaction is verified and recorded accurately, preventing issues like double-spending. This decentralized agreement fosters trust among participants, as no single entity controls the network. The consensus process is vital for maintaining the integrity and security of the blockchain, allowing it to function effectively as a reliable source of truth without a central authority.