Alternative splicing is pervasive gene regulatory mechanism utilized by both host and virus to expand genomic coding capacity. In this dissertation, an overarching goal is to understand how the regulation of alternative splicing ultimately influences viral replication. I investigate this question by examining the mechanism by which influenza A virus (IAV) M segment RNA is spliced. I show that host factors hnRNP K and NS1-BP along with IAV protein NS1 regulate M segment splicing through a novel post-transcriptional splicing mechanism that is dependent on RNA localization to nuclear speckles. In characterization of this mechanism I find that hnRNP K and NS1-BP co-regulate host transcripts through potentially similar mechanisms. Moreover, I observe that host splicing events regulated by hnRNP K and NS1-BP are subject to mis-splicing upon IAV infection. Motivated by these observations, I go on to investigate how host alternative splicing is regulated during IAV infection and whether these alternative splicing changes have any functional significance to viral replication. I show that infection with IAV H1N1 induces transcriptome-wide splicing changes, many of which are regulated by hnRNP K. I then go on to show that subset of these hnRNP K/IAV-sensitive splicing events are important to viral replication via siRNA screening and splice-blocking antisense oligonucleotide experiments. Together, the data I present here introduces novel insight into how both host and viral alternative splicing regulation influences IAV replication.