Peercoin, also known as Peer-to-Peer Coin, PP Coin, or PPC, is a cryptocurrency utilizing both proof-of-stake and proof-of-work systems. It is notable as the first cryptocurrency to implement the proof-of-stake consensus mechanism.

Peercoin is based on an August 2012 paper that listed the authors as Scott Nadal and Sunny King. King, who also created Primecoin, is a pseudonym.

The Peercoin source code is distributed under the MIT/X11 software license.^{[citation needed]}

Peercoin uses both the proof-of-work and proof-of-stake algorithms. Both are used to spread the distribution of new coins. During its primary years, Peercoin relied heavily on PoW, although there has now been a transition to PoS. Proof-of-stake is used to secure the network: The chain with longest PoS coin age wins in case of a blockchain split-up.

To target a global 1% annual inflation rate, individual stakes typically receive a 3 - 5% annual reward, as only a minority of coins are actively staked. This reward is based on a dynamic portion (75% of the reward) and a static portion (25% of the reward). The dynamic portion of the reward for an individual stake is based on the number of coins, their unspent age, and degree of global staking participation. Stake-for-Stake, periods of low (high) global staking participation will result in a higher (lower) dynamic reward. The static portion of the reward is based on the fraction of the existing total coin supply minted on average in a year, and is awarded regardless of stake size. As of December 2024, the static reward for a proof-of-stake block is approximately 1.4 PPC.

A transaction fee prevents spam and is burned (instead of being collected by a miner), benefiting the overall network.