diff --git a/src/Common/Library.fs b/src/Common/Library.fs
index bf6f9bd..03308b7 100644
--- a/src/Common/Library.fs
+++ b/src/Common/Library.fs
@@ -19,6 +19,10 @@ type Op =
     | NE
     /// Between (BETWEEN)
     | BT
+    /// In (IN)
+    | IN
+    // Array Contains/Exists (PostgreSQL: |? SQLite: EXISTS / json_each / IN)
+    //| AEX
     /// Exists (IS NOT NULL)
     | EX
     /// Does Not Exist (IS NULL)
@@ -33,6 +37,7 @@ type Op =
         | LE -> "<="
         | NE -> "<>"
         | BT -> "BETWEEN"
+        | IN -> "IN"
         | EX -> "IS NOT NULL"
         | NEX -> "IS NULL"
 
@@ -89,6 +94,10 @@ type Field = {
     static member BT name (min: obj) (max: obj) =
         { Name = name; Op = BT; Value = [ min; max ]; ParameterName = None; Qualifier = None }
     
+    /// Create an IN field criterion
+    static member IN name (values: obj seq) =
+        { Name = name; Op = IN; Value = values; ParameterName = None; Qualifier = None }
+        
     /// Create an exists (IS NOT NULL) field criterion
     static member EX name =
         { Name = name; Op = EX; Value = obj (); ParameterName = None; Qualifier = None }
diff --git a/src/Postgres/Library.fs b/src/Postgres/Library.fs
index 4095549..fd37426 100644
--- a/src/Postgres/Library.fs
+++ b/src/Postgres/Library.fs
@@ -96,6 +96,13 @@ module Parameters =
                            parameterFor (List.head values) (fun v -> Sql.parameter (NpgsqlParameter($"{p}min", v))))
                     yield ($"{p}max",
                            parameterFor (List.last values) (fun v -> Sql.parameter (NpgsqlParameter($"{p}max", v))))
+                | IN ->
+                    let p = name.Derive it.ParameterName
+                    yield!
+                        it.Value :?> obj seq
+                        |> Seq.mapi (fun idx v ->
+                            let paramName = $"{p}_{idx}" 
+                            paramName, Sql.parameter (NpgsqlParameter(paramName, v)))
                 | _ ->
                     let p = name.Derive it.ParameterName
                     yield (p, parameterFor it.Value (fun v -> Sql.parameter (NpgsqlParameter(p, v)))) })
@@ -138,6 +145,10 @@ module Query =
                 let param, value =
                     match it.Op with
                     | BT -> $"{p}min AND {p}max", (it.Value :?> obj list)[0]
+                    | IN ->
+                        let values     = it.Value :?> obj seq
+                        let paramNames = values |> Seq.mapi (fun idx _ -> $"{p}_{idx}") |> String.concat ", "
+                        $"({paramNames})", defaultArg (Seq.tryHead values) (obj ())
                     | _  -> p, it.Value
                 if isNumeric value then
                     $"({it.Path PostgreSQL})::numeric {it.Op} {param}"
diff --git a/src/Sqlite/Library.fs b/src/Sqlite/Library.fs
index d34d3f1..4458ccb 100644
--- a/src/Sqlite/Library.fs
+++ b/src/Sqlite/Library.fs
@@ -42,6 +42,10 @@ module Query =
             | BT ->
                 let p = name.Derive it.ParameterName
                 $"{it.Path SQLite} {it.Op} {p}min AND {p}max"
+            | IN ->
+                let p          = name.Derive it.ParameterName
+                let paramNames = it.Value :?> obj seq |> Seq.mapi (fun idx _ -> $"{p}_{idx}") |> String.concat ", "
+                $"{it.Path SQLite} {it.Op} ({paramNames})"
             | _ -> $"{it.Path SQLite} {it.Op} {name.Derive it.ParameterName}")
         |> String.concat $" {howMatched} "
 
@@ -110,6 +114,9 @@ module Parameters =
                     let values = it.Value :?> obj list
                     yield SqliteParameter($"{p}min", List.head values)
                     yield SqliteParameter($"{p}max", List.last values)
+                | IN ->
+                    let p = name.Derive it.ParameterName
+                    yield! it.Value :?> obj seq |> Seq.mapi (fun idx v -> SqliteParameter($"{p}_{idx}", v))
                 | _ -> yield SqliteParameter(name.Derive it.ParameterName, it.Value) })
         |> Seq.collect id
         |> Seq.append parameters
diff --git a/src/Tests/PostgresTests.fs b/src/Tests/PostgresTests.fs
index 497e712..fd83d72 100644
--- a/src/Tests/PostgresTests.fs
+++ b/src/Tests/PostgresTests.fs
@@ -177,6 +177,18 @@ let queryTests = testList "Query" [
                 "(data->>'aField')::numeric BETWEEN @field0min AND @field0max AND data->>'anotherField' BETWEEN @field1min AND @field1max"
                 "WHERE clause not correct"
         }
+        test "succeeds for a field with an IN operator with alphanumeric values" {
+            Expect.equal
+                (Query.whereByFields All [ Field.IN "this" [ "a"; "b"; "c" ] ])
+                "data->>'this' IN (@field0_0, @field0_1, @field0_2)"
+                "WHERE clause not correct"
+        }
+        test "succeeds for a field with an IN operator with numeric values" {
+            Expect.equal
+                (Query.whereByFields All [ Field.IN "this" [ 7; 14; 21 ] ])
+                "(data->>'this')::numeric IN (@field0_0, @field0_1, @field0_2)"
+                "WHERE clause not correct"
+        }
     ]
     testList "whereById" [
         test "succeeds for numeric ID" {
diff --git a/src/Tests/SqliteTests.fs b/src/Tests/SqliteTests.fs
index 1a2e71d..1cf4aa8 100644
--- a/src/Tests/SqliteTests.fs
+++ b/src/Tests/SqliteTests.fs
@@ -51,6 +51,12 @@ let queryTests = testList "Query" [
                 "data->>'aField' BETWEEN @field0min AND @field0max AND data->>'anotherField' BETWEEN @field1min AND @field1max"
                 "WHERE clause not correct"
         }
+        test "succeeds for a field with an IN operator" {
+            Expect.equal
+                (Query.whereByFields All [ Field.IN "this" [ "a"; "b"; "c" ] ])
+                "data->>'this' IN (@field0_0, @field0_1, @field0_2)"
+                "WHERE clause not correct"
+        }
     ]
     test "whereById succeeds" {
         Expect.equal (Query.whereById "@id") "data->>'Id' = @id" "WHERE clause not correct"