Segregated Witness (SegWit) is a protocol upgrade that was introduced to improve the scalability, security, and efficiency of blockchain networks like Litecoin. SegWit separates the transaction's signature data (the "witness" data) from the transaction itself, thereby freeing up space in each block. This allows for more transactions to fit into a single block, effectively increasing the block's capacity without increasing its size.

In the Litecoin ecosystem, SegWit was activated in May 2017. Its introduction had several positive impacts. First, it helped reduce transaction fees by increasing the number of transactions that can be processed per block. This made Litecoin more cost-effective for users, especially for smaller transactions.

Second, SegWit enhanced transaction speed and network efficiency. By optimizing how data is stored in each block, it reduced network congestion, leading to faster transaction confirmations.

SegWit also enabled the implementation of the Lightning Network on Litecoin. The Lightning Network allows for off-chain transactions, which are faster and cheaper, further enhancing Litecoin’s scalability.

Finally, SegWit improved the overall **security** of the network by addressing transaction malleability, a vulnerability where the transaction ID could be altered before confirmation. This increased trust in Litecoin’s infrastructure, making it more attractive for developers and users.