This document introduces .NET for Apache Spark, which allows .NET developers to use the Apache Spark analytics engine for big data and machine learning. It discusses why .NET support is needed for Apache Spark given that much business logic is written in .NET. It provides an overview of .NET for Apache Spark's capabilities including Spark DataFrames, machine learning, and performance that is on par or faster than PySpark. Examples and demos are shown. Future plans are discussed to improve the tooling, expand programming experiences, and provide out-of-box experiences on platforms like Azure HDInsight and Azure Databricks. Readers are encouraged to engage with the open source project and provide feedback.