diff --git a/crates/wasi-common/src/error.rs b/crates/wasi-common/src/error.rs
new file mode 100644
index 0000000000..932519200d
--- /dev/null
+++ b/crates/wasi-common/src/error.rs
@@ -0,0 +1,90 @@
+use thiserror::Error;
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Internal error type for the `wasi-common` crate.
+/// Contains variants of the WASI `$errno` type are added according to what is actually used internally by
+/// the crate. Not all values are represented presently,
+#[derive(Debug, Error)]
+pub enum Error {
+    #[error(display = "Wiggle GuestError: {0}")]
+    Guest(#[from] wiggle::GuestError),
+    #[error(display = "TryFromIntError: {0}")]
+    TryFromInt(#[from] std::num::TryFromIntError),
+    #[error(display = "Utf8Error: {0}")]
+    Utf8(#[from] std::str::Utf8Error),
+
+    // Below this, all variants are from the `$errno` type:
+    /// Errno::TooBig: Argument list too long
+    #[error(display = "TooBig: Argument list too long")]
+    TooBig,
+    /// Errno::Acces: Permission denied
+    #[error(display = "Acces: Permission denied")]
+    Acces,
+    /// Errno::Badf: Bad file descriptor
+    #[error(display = "Badf: Bad file descriptor")]
+    Badf,
+    /// Errno::Exist: File exists
+    #[error(display = "Exist: File exists")]
+    Exist,
+    /// Errno::Fault: Bad address
+    #[error(display = "Fault: Bad address")]
+    Fault,
+    /// Errno::Fbig: File too large
+    #[error(display = "Fbig: File too large")]
+    Fbig,
+    /// Errno::Ilseq: Illegal byte sequence
+    #[error(display = "Ilseq: Illegal byte sequence")]
+    Ilseq,
+    /// Errno::Inval: Invalid argument
+    #[error(display = "Inval: Invalid argument")]
+    Inval,
+    /// Errno::Io: I/O error
+    #[error(display = "Io: I/o error")]
+    Io,
+    /// Errno::Isdir: Is a directory
+    #[error(display = "Isdir: Is a directory")]
+    Isdir,
+    /// Errno::Loop: Too many levels of symbolic links
+    #[error(display = "Loop: Too many levels of symbolic links")]
+    Loop,
+    /// Errno::Mfile: File descriptor value too large
+    #[error(display = "Mfile: File descriptor value too large")]
+    Mfile,
+    /// Errno::Mlink: Too many links
+    #[error(display = "Mlink: Too many links")]
+    Mlink,
+    /// Errno::Nametoolong: Filename too long
+    #[error(display = "Nametoolong: Filename too long")]
+    Nametoolong,
+    /// Errno::Noent: No such file or directory
+    #[error(display = "Noent: No such file or directory")]
+    Noent,
+    /// Errno::Nospc: No space left on device
+    #[error(display = "Nospc: No space left on device")]
+    Nospc,
+    /// Errno::Notempty: Directory not empty.
+    #[error(display = "Notempty: Directory not empty")]
+    Notempty,
+    /// Errno::Notsup: Not supported, or operation not supported on socket.
+    #[error(display = "Notsup: Not supported, or operation not supported on socket")]
+    Notsup,
+    /// Errno::Overflow: Value too large to be stored in data type.
+    #[error(display = "Overflow: Value too large to be stored in data type")]
+    Overflow,
+    /// Errno::Perm: Operation not permitted
+    #[error(display = "Perm: Operation not permitted")]
+    Perm,
+    /// Errno::Spipe: Invalid seek
+    #[error(display = "Spipe: Invalid seek")]
+    Spipe,
+    /// Errno::Notcapable: Extension: Capabilities insufficient
+    #[error(display = "Notcapable: cabailities insufficient")]
+    Notcapable,
+}
+
+impl From<std::convert::Infallible> for Error {
+    fn from(_err: std::convert::Infallible) -> Self {
+        unreachable!("should be impossible: From<Infallible>")
+    }
+}
diff --git a/crates/wasi-common/src/lib.rs b/crates/wasi-common/src/lib.rs
index 65b5ea047d..76e64bb3c0 100644
--- a/crates/wasi-common/src/lib.rs
+++ b/crates/wasi-common/src/lib.rs
@@ -23,6 +23,7 @@
 
 mod ctx;
 mod entry;
+mod error;
 mod fdpool;
 pub mod fs;
 mod handle;
@@ -36,6 +37,7 @@ pub mod virtfs;
 pub mod wasi;
 
 pub use ctx::{WasiCtx, WasiCtxBuilder, WasiCtxBuilderError};
+pub use error::{Error, Result};
 pub use handle::{Handle, HandleRights};
 pub use sys::osdir::OsDir;
 pub use sys::osfile::OsFile;