diff --git a/.travis.yml b/.travis.yml
index f0cc6fe..fa4b2c4 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -28,12 +28,9 @@ script:
   - cargo build --features sqlcipher
   - cargo build --features "bundled sqlcipher"
   - cargo test
-  - cargo test --features backup
-  - cargo test --features blob
-  - cargo test --features collation
-  - cargo test --features functions
-  - cargo test --features hooks
-  - cargo test --features limits
+  - cargo test --features "backup blob"
+  - cargo test --features "collation functions"
+  - cargo test --features "hooks limits"
   - cargo test --features load_extension
   - cargo test --features trace
   - cargo test --features chrono
@@ -43,7 +40,7 @@ script:
   - cargo test --features sqlcipher
   - cargo test --features i128_blob
   - cargo test --features uuid
-  - cargo test --features "unlock_notify bundled"
+  - cargo test --features "bundled unlock_notify window"
   - cargo test --features "array bundled csvtab vtab"
   - cargo test --features "backup blob chrono collation csvtab functions hooks limits load_extension serde_json trace url uuid vtab"
   - cargo test --features "backup blob chrono collation csvtab functions hooks limits load_extension serde_json trace url uuid vtab buildtime_bindgen"
diff --git a/Cargo.toml b/Cargo.toml
index be6cdc1..eefe176 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -49,6 +49,8 @@ csvtab = ["csv", "vtab"]
 array = ["vtab"]
 # session extension: 3.13.0
 session = ["libsqlite3-sys/session", "hooks"]
+# window functions: 3.25.0
+window = ["functions"]
 
 [dependencies]
 time = "0.1.0"
diff --git a/src/functions.rs b/src/functions.rs
index 6a0f54a..06f681d 100644
--- a/src/functions.rs
+++ b/src/functions.rs
@@ -226,6 +226,22 @@ where
     fn finalize(&self, _: Option<A>) -> Result<T>;
 }
 
+/// WindowAggregate is the callback interface for user-defined aggregate window
+/// function.
+#[cfg(feature = "window")]
+pub trait WindowAggregate<A, T>: Aggregate<A, T>
+where
+    A: RefUnwindSafe + UnwindSafe,
+    T: ToSql,
+{
+    /// Returns the current value of the aggregate. Unlike xFinal, the
+    /// implementation should not delete any context.
+    fn value(&self, _: Option<&A>) -> Result<T>;
+
+    /// Removes a row from the current window.
+    fn inverse(&self, _: &mut Context<'_>, _: &mut A) -> Result<()>;
+}
+
 impl Connection {
     /// Attach a user-defined scalar function to this database connection.
     ///
@@ -294,6 +310,24 @@ impl Connection {
             .create_aggregate_function(fn_name, n_arg, deterministic, aggr)
     }
 
+    #[cfg(feature = "window")]
+    pub fn create_window_function<A, W, T>(
+        &self,
+        fn_name: &str,
+        n_arg: c_int,
+        deterministic: bool,
+        aggr: W,
+    ) -> Result<()>
+    where
+        A: RefUnwindSafe + UnwindSafe,
+        W: WindowAggregate<A, T>,
+        T: ToSql,
+    {
+        self.db
+            .borrow_mut()
+            .create_window_function(fn_name, n_arg, deterministic, aggr)
+    }
+
     /// Removes a user-defined function from this database connection.
     ///
     /// `fn_name` and `n_arg` should match the name and number of arguments
@@ -386,105 +420,6 @@ impl InnerConnection {
         D: Aggregate<A, T>,
         T: ToSql,
     {
-        unsafe fn aggregate_context<A>(
-            ctx: *mut sqlite3_context,
-            bytes: usize,
-        ) -> Option<*mut *mut A> {
-            let pac = ffi::sqlite3_aggregate_context(ctx, bytes as c_int) as *mut *mut A;
-            if pac.is_null() {
-                return None;
-            }
-            Some(pac)
-        }
-
-        unsafe extern "C" fn call_boxed_step<A, D, T>(
-            ctx: *mut sqlite3_context,
-            argc: c_int,
-            argv: *mut *mut sqlite3_value,
-        ) where
-            A: RefUnwindSafe + UnwindSafe,
-            D: Aggregate<A, T>,
-            T: ToSql,
-        {
-            let pac = match aggregate_context(ctx, ::std::mem::size_of::<*mut A>()) {
-                Some(pac) => pac,
-                None => {
-                    ffi::sqlite3_result_error_nomem(ctx);
-                    return;
-                }
-            };
-
-            let r = catch_unwind(|| {
-                let boxed_aggr: *mut D = ffi::sqlite3_user_data(ctx) as *mut D;
-                assert!(
-                    !boxed_aggr.is_null(),
-                    "Internal error - null aggregate pointer"
-                );
-                if (*pac as *mut A).is_null() {
-                    *pac = Box::into_raw(Box::new((*boxed_aggr).init()));
-                }
-                let mut ctx = Context {
-                    ctx,
-                    args: slice::from_raw_parts(argv, argc as usize),
-                };
-                (*boxed_aggr).step(&mut ctx, &mut **pac)
-            });
-            let r = match r {
-                Err(_) => {
-                    report_error(ctx, &Error::UnwindingPanic);
-                    return;
-                }
-                Ok(r) => r,
-            };
-            match r {
-                Ok(_) => {}
-                Err(err) => report_error(ctx, &err),
-            };
-        }
-
-        unsafe extern "C" fn call_boxed_final<A, D, T>(ctx: *mut sqlite3_context)
-        where
-            A: RefUnwindSafe + UnwindSafe,
-            D: Aggregate<A, T>,
-            T: ToSql,
-        {
-            // Within the xFinal callback, it is customary to set N=0 in calls to
-            // sqlite3_aggregate_context(C,N) so that no pointless memory allocations occur.
-            let a: Option<A> = match aggregate_context(ctx, 0) {
-                Some(pac) => {
-                    if (*pac as *mut A).is_null() {
-                        None
-                    } else {
-                        let a = Box::from_raw(*pac);
-                        Some(*a)
-                    }
-                }
-                None => None,
-            };
-
-            let r = catch_unwind(|| {
-                let boxed_aggr: *mut D = ffi::sqlite3_user_data(ctx) as *mut D;
-                assert!(
-                    !boxed_aggr.is_null(),
-                    "Internal error - null aggregate pointer"
-                );
-                (*boxed_aggr).finalize(a)
-            });
-            let t = match r {
-                Err(_) => {
-                    report_error(ctx, &Error::UnwindingPanic);
-                    return;
-                }
-                Ok(r) => r,
-            };
-            let t = t.as_ref().map(|t| ToSql::to_sql(t));
-            match t {
-                Ok(Ok(ref value)) => set_result(ctx, value),
-                Ok(Err(err)) => report_error(ctx, &err),
-                Err(err) => report_error(ctx, err),
-            }
-        }
-
         let boxed_aggr: *mut D = Box::into_raw(Box::new(aggr));
         let c_name = str_to_cstring(fn_name)?;
         let mut flags = ffi::SQLITE_UTF8;
@@ -507,6 +442,42 @@ impl InnerConnection {
         self.decode_result(r)
     }
 
+    #[cfg(feature = "window")]
+    fn create_window_function<A, W, T>(
+        &mut self,
+        fn_name: &str,
+        n_arg: c_int,
+        deterministic: bool,
+        aggr: W,
+    ) -> Result<()>
+    where
+        A: RefUnwindSafe + UnwindSafe,
+        W: WindowAggregate<A, T>,
+        T: ToSql,
+    {
+        let boxed_aggr: *mut W = Box::into_raw(Box::new(aggr));
+        let c_name = str_to_cstring(fn_name)?;
+        let mut flags = ffi::SQLITE_UTF8;
+        if deterministic {
+            flags |= ffi::SQLITE_DETERMINISTIC;
+        }
+        let r = unsafe {
+            ffi::sqlite3_create_window_function(
+                self.db(),
+                c_name.as_ptr(),
+                n_arg,
+                flags,
+                boxed_aggr as *mut c_void,
+                Some(call_boxed_step::<A, W, T>),
+                Some(call_boxed_final::<A, W, T>),
+                Some(call_boxed_value::<A, W, T>),
+                Some(call_boxed_inverse::<A, W, T>),
+                Some(free_boxed_value::<W>),
+            )
+        };
+        self.decode_result(r)
+    }
+
     fn remove_function(&mut self, fn_name: &str, n_arg: c_int) -> Result<()> {
         let c_name = str_to_cstring(fn_name)?;
         let r = unsafe {
@@ -526,6 +497,189 @@ impl InnerConnection {
     }
 }
 
+unsafe fn aggregate_context<A>(ctx: *mut sqlite3_context, bytes: usize) -> Option<*mut *mut A> {
+    let pac = ffi::sqlite3_aggregate_context(ctx, bytes as c_int) as *mut *mut A;
+    if pac.is_null() {
+        return None;
+    }
+    Some(pac)
+}
+
+unsafe extern "C" fn call_boxed_step<A, D, T>(
+    ctx: *mut sqlite3_context,
+    argc: c_int,
+    argv: *mut *mut sqlite3_value,
+) where
+    A: RefUnwindSafe + UnwindSafe,
+    D: Aggregate<A, T>,
+    T: ToSql,
+{
+    let pac = match aggregate_context(ctx, ::std::mem::size_of::<*mut A>()) {
+        Some(pac) => pac,
+        None => {
+            ffi::sqlite3_result_error_nomem(ctx);
+            return;
+        }
+    };
+
+    let r = catch_unwind(|| {
+        let boxed_aggr: *mut D = ffi::sqlite3_user_data(ctx) as *mut D;
+        assert!(
+            !boxed_aggr.is_null(),
+            "Internal error - null aggregate pointer"
+        );
+        if (*pac as *mut A).is_null() {
+            *pac = Box::into_raw(Box::new((*boxed_aggr).init()));
+        }
+        let mut ctx = Context {
+            ctx,
+            args: slice::from_raw_parts(argv, argc as usize),
+        };
+        (*boxed_aggr).step(&mut ctx, &mut **pac)
+    });
+    let r = match r {
+        Err(_) => {
+            report_error(ctx, &Error::UnwindingPanic);
+            return;
+        }
+        Ok(r) => r,
+    };
+    match r {
+        Ok(_) => {}
+        Err(err) => report_error(ctx, &err),
+    };
+}
+
+#[cfg(feature = "window")]
+unsafe extern "C" fn call_boxed_inverse<A, W, T>(
+    ctx: *mut sqlite3_context,
+    argc: c_int,
+    argv: *mut *mut sqlite3_value,
+) where
+    A: RefUnwindSafe + UnwindSafe,
+    W: WindowAggregate<A, T>,
+    T: ToSql,
+{
+    let pac = match aggregate_context(ctx, ::std::mem::size_of::<*mut A>()) {
+        Some(pac) => pac,
+        None => {
+            ffi::sqlite3_result_error_nomem(ctx);
+            return;
+        }
+    };
+
+    let r = catch_unwind(|| {
+        let boxed_aggr: *mut W = ffi::sqlite3_user_data(ctx) as *mut W;
+        assert!(
+            !boxed_aggr.is_null(),
+            "Internal error - null aggregate pointer"
+        );
+        let mut ctx = Context {
+            ctx,
+            args: slice::from_raw_parts(argv, argc as usize),
+        };
+        (*boxed_aggr).inverse(&mut ctx, &mut **pac)
+    });
+    let r = match r {
+        Err(_) => {
+            report_error(ctx, &Error::UnwindingPanic);
+            return;
+        }
+        Ok(r) => r,
+    };
+    match r {
+        Ok(_) => {}
+        Err(err) => report_error(ctx, &err),
+    };
+}
+
+unsafe extern "C" fn call_boxed_final<A, D, T>(ctx: *mut sqlite3_context)
+where
+    A: RefUnwindSafe + UnwindSafe,
+    D: Aggregate<A, T>,
+    T: ToSql,
+{
+    // Within the xFinal callback, it is customary to set N=0 in calls to
+    // sqlite3_aggregate_context(C,N) so that no pointless memory allocations occur.
+    let a: Option<A> = match aggregate_context(ctx, 0) {
+        Some(pac) => {
+            if (*pac as *mut A).is_null() {
+                None
+            } else {
+                let a = Box::from_raw(*pac);
+                Some(*a)
+            }
+        }
+        None => None,
+    };
+
+    let r = catch_unwind(|| {
+        let boxed_aggr: *mut D = ffi::sqlite3_user_data(ctx) as *mut D;
+        assert!(
+            !boxed_aggr.is_null(),
+            "Internal error - null aggregate pointer"
+        );
+        (*boxed_aggr).finalize(a)
+    });
+    let t = match r {
+        Err(_) => {
+            report_error(ctx, &Error::UnwindingPanic);
+            return;
+        }
+        Ok(r) => r,
+    };
+    let t = t.as_ref().map(|t| ToSql::to_sql(t));
+    match t {
+        Ok(Ok(ref value)) => set_result(ctx, value),
+        Ok(Err(err)) => report_error(ctx, &err),
+        Err(err) => report_error(ctx, err),
+    }
+}
+
+#[cfg(feature = "window")]
+unsafe extern "C" fn call_boxed_value<A, W, T>(ctx: *mut sqlite3_context)
+where
+    A: RefUnwindSafe + UnwindSafe,
+    W: WindowAggregate<A, T>,
+    T: ToSql,
+{
+    // Within the xValue callback, it is customary to set N=0 in calls to
+    // sqlite3_aggregate_context(C,N) so that no pointless memory allocations occur.
+    let a: Option<&A> = match aggregate_context(ctx, 0) {
+        Some(pac) => {
+            if (*pac as *mut A).is_null() {
+                None
+            } else {
+                let a = &**pac;
+                Some(a)
+            }
+        }
+        None => None,
+    };
+
+    let r = catch_unwind(|| {
+        let boxed_aggr: *mut W = ffi::sqlite3_user_data(ctx) as *mut W;
+        assert!(
+            !boxed_aggr.is_null(),
+            "Internal error - null aggregate pointer"
+        );
+        (*boxed_aggr).value(a)
+    });
+    let t = match r {
+        Err(_) => {
+            report_error(ctx, &Error::UnwindingPanic);
+            return;
+        }
+        Ok(r) => r,
+    };
+    let t = t.as_ref().map(|t| ToSql::to_sql(t));
+    match t {
+        Ok(Ok(ref value)) => set_result(ctx, value),
+        Ok(Err(err)) => report_error(ctx, &err),
+        Err(err) => report_error(ctx, err),
+    }
+}
+
 #[cfg(test)]
 mod test {
     use regex;
@@ -535,6 +689,8 @@ mod test {
     use std::os::raw::c_double;
 
     use crate::functions::{Aggregate, Context};
+    #[cfg(feature = "window")]
+    use crate::functions::WindowAggregate;
     use crate::{Connection, Error, Result, NO_PARAMS};
 
     fn half(ctx: &Context<'_>) -> Result<c_double> {
@@ -752,4 +908,58 @@ mod test {
         let result: i64 = db.query_row(single_sum, NO_PARAMS, |r| r.get(0)).unwrap();
         assert_eq!(2, result);
     }
+
+    #[cfg(feature = "window")]
+    impl WindowAggregate<i64, Option<i64>> for Sum {
+        fn inverse(&self, ctx: &mut Context<'_>, sum: &mut i64) -> Result<()> {
+            *sum -= ctx.get::<i64>(0)?;
+            Ok(())
+        }
+
+        fn value(&self, sum: Option<&i64>) -> Result<Option<i64>> {
+            Ok(sum.copied())
+        }
+    }
+
+    #[test]
+    #[cfg(feature = "window")]
+    fn test_window() {
+        use fallible_iterator::FallibleIterator;
+
+        let db = Connection::open_in_memory().unwrap();
+        db.create_window_function("sumint", 1, true, Sum).unwrap();
+        db.execute_batch(
+            "CREATE TABLE t3(x, y);
+             INSERT INTO t3 VALUES('a', 4),
+                     ('b', 5),
+                     ('c', 3),
+                     ('d', 8),
+                     ('e', 1);",
+        )
+        .unwrap();
+
+        let mut stmt = db
+            .prepare(
+                "SELECT x, sumint(y) OVER (
+                   ORDER BY x ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING
+                 ) AS sum_y
+                 FROM t3 ORDER BY x;",
+            )
+            .unwrap();
+
+        let results: Vec<(String, i64)> = stmt
+            .query(NO_PARAMS)
+            .unwrap()
+            .map(|row| Ok((row.get("x")?, row.get("sum_y")?)))
+            .collect()
+            .unwrap();
+        let expected = vec![
+            ("a".to_owned(), 9),
+            ("b".to_owned(), 12),
+            ("c".to_owned(), 16),
+            ("d".to_owned(), 12),
+            ("e".to_owned(), 9),
+        ];
+        assert_eq!(expected, results);
+    }
 }