diff --git a/src/ascii_char.rs b/src/ascii_char.rs
index 39f2ceb..3fc6e75 100644
--- a/src/ascii_char.rs
+++ b/src/ascii_char.rs
@@ -794,8 +794,8 @@ macro_rules! impl_into_partial_eq_ord {
     ($wider:ty, $to_wider:expr) => {
         impl From<AsciiChar> for $wider {
             #[inline]
-            fn from(a: AsciiChar) -> $wider {
-                $to_wider(a)
+            fn from(ascii: AsciiChar) -> $wider {
+                $to_wider(ascii)
             }
         }
         impl PartialEq<$wider> for AsciiChar {
diff --git a/src/ascii_str.rs b/src/ascii_str.rs
index bfdf54e..942e79f 100644
--- a/src/ascii_str.rs
+++ b/src/ascii_str.rs
@@ -10,6 +10,8 @@ use core::slice::{self, Iter, IterMut, SliceIndex};
 use std::error::Error;
 #[cfg(feature = "std")]
 use std::ffi::CStr;
+#[cfg(feature = "std")]
+use std::ffi::OsStr;
 
 use ascii_char::AsciiChar;
 #[cfg(feature = "alloc")]
@@ -407,6 +409,8 @@ macro_rules! impl_partial_eq {
     };
 }
 
+#[cfg(feature = "std")]
+impl_partial_eq! {OsStr}
 impl_partial_eq! {str}
 impl_partial_eq! {[u8]}
 impl_partial_eq! {[AsciiChar]}
@@ -433,6 +437,13 @@ impl AsRef<str> for AsciiStr {
         self.as_str()
     }
 }
+#[cfg(feature = "std")]
+impl AsRef<OsStr> for AsciiStr {
+    #[inline]
+    fn as_ref(&self) -> &OsStr {
+        self.as_str().as_ref()
+    }
+}
 impl AsRef<[AsciiChar]> for AsciiStr {
     #[inline]
     fn as_ref(&self) -> &[AsciiChar] {
@@ -524,6 +535,13 @@ impl<'a> From<&'a AsciiStr> for &'a str {
         astr.as_str()
     }
 }
+#[cfg(feature = "std")]
+impl<'a> From<&'a AsciiStr> for &'a OsStr {
+    #[inline]
+    fn from(astr: &AsciiStr) -> &OsStr {
+        astr.as_ref()
+    }
+}
 macro_rules! widen_box {
     ($wider: ty) => {
         #[cfg(feature = "alloc")]
@@ -539,6 +557,8 @@ macro_rules! widen_box {
 widen_box! {[AsciiChar]}
 widen_box! {[u8]}
 widen_box! {str}
+#[cfg(feature = "std")]
+widen_box! {OsStr}
 
 // allows &AsciiChar to be used by generic AsciiString Extend and FromIterator
 impl AsRef<AsciiStr> for AsciiChar {
@@ -1291,6 +1311,25 @@ impl AsAsciiStr for CStr {
     }
 }
 
+#[cfg(feature = "std")]
+impl AsAsciiStr for OsStr {
+    type Inner = u8;
+    fn slice_ascii<R>(&self, range: R) -> Result<&AsciiStr, AsAsciiStrError>
+    where
+        R: SliceIndex<[u8], Output = [u8]>,
+    {
+        self.as_encoded_bytes().slice_ascii(range)
+    }
+    fn as_ascii_str(&self) -> Result<&AsciiStr, AsAsciiStrError> {
+        self.as_encoded_bytes().as_ascii_str()
+    }
+    #[inline]
+    unsafe fn as_ascii_str_unchecked(&self) -> &AsciiStr {
+        // SAFETY: Caller guarantees `self` does not contain non-ascii characters
+        unsafe { self.as_encoded_bytes().as_ascii_str_unchecked() }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::{AsAsciiStr, AsAsciiStrError, AsMutAsciiStr, AsciiStr};
@@ -1367,6 +1406,19 @@ mod tests {
         assert_eq!(generic_mut(ascii_str_mut), Ok(&mut *ascii_str_mut_2));
     }
 
+    #[cfg(feature = "std")]
+    #[test]
+    fn osstr_as_ascii_str() {
+        use std::ffi::OsStr;
+        fn generic<C: AsAsciiStr + ?Sized>(c: &C) -> Result<&AsciiStr, AsAsciiStrError> {
+            c.as_ascii_str()
+        }
+        let arr = [AsciiChar::A];
+        let ascii_str: &AsciiStr = arr.as_ref().into();
+        let os_str = OsStr::new(ascii_str);
+        assert_eq!(generic(&*os_str), Ok(ascii_str));
+    }
+
     #[test]
     fn as_ascii_str() {
         macro_rules! err {{$i:expr} => {Err(AsAsciiStrError($i))}}
diff --git a/src/ascii_string.rs b/src/ascii_string.rs
index b6d2b0b..510d1b5 100644
--- a/src/ascii_string.rs
+++ b/src/ascii_string.rs
@@ -15,6 +15,8 @@ use core::str::FromStr;
 use std::error::Error;
 #[cfg(feature = "std")]
 use std::ffi::{CStr, CString};
+#[cfg(feature = "std")]
+use std::ffi::OsStr;
 
 use ascii_char::AsciiChar;
 use ascii_str::{AsAsciiStr, AsAsciiStrError, AsciiStr};
@@ -451,6 +453,22 @@ impl PartialEq<AsciiString> for str {
     }
 }
 
+#[cfg(feature = "std")]
+impl PartialEq<OsStr> for AsciiString {
+    #[inline]
+    fn eq(&self, other: &OsStr) -> bool {
+        **self == *other
+    }
+}
+
+#[cfg(feature = "std")]
+impl PartialEq<AsciiString> for OsStr {
+    #[inline]
+    fn eq(&self, other: &AsciiString) -> bool {
+        **other == *self
+    }
+}
+
 macro_rules! impl_eq {
     ($lhs:ty, $rhs:ty) => {
         impl PartialEq<$rhs> for $lhs {
@@ -470,6 +488,10 @@ impl_eq! { &AsciiStr, AsciiString }
 impl_eq! { AsciiString, &AsciiStr }
 impl_eq! { &str, AsciiString }
 impl_eq! { AsciiString, &str }
+#[cfg(feature = "std")]
+impl_eq! { &OsStr, AsciiString }
+#[cfg(feature = "std")]
+impl_eq! { AsciiString, &OsStr }
 
 impl Borrow<AsciiStr> for AsciiString {
     #[inline]
@@ -619,6 +641,14 @@ impl AsRef<str> for AsciiString {
     }
 }
 
+#[cfg(feature = "std")]
+impl AsRef<OsStr> for AsciiString {
+    #[inline]
+    fn as_ref(&self) -> &OsStr {
+        self.as_str().as_ref()
+    }
+}
+
 impl AsMut<AsciiStr> for AsciiString {
     #[inline]
     fn as_mut(&mut self) -> &mut AsciiStr {