diff --git a/proto/substrait/algebra.proto b/proto/substrait/algebra.proto
index 60c1d2090..578eb381d 100644
--- a/proto/substrait/algebra.proto
+++ b/proto/substrait/algebra.proto
@@ -342,6 +342,34 @@ message ExchangeRel {
   }
 }
 
+// Duplicates records, possibly switching output expressions between each duplicate.
+// Default output is all of the fields declared followed by one int64 field that contains the
+// duplicate_id which is a zero-index ordinal of which duplicate of the original record this
+// corresponds to.
+message ExpandRel {
+  RelCommon common = 1;
+  Rel input = 2;
+  repeated ExpandField fields = 4;
+
+  message ExpandField {
+    oneof field_type {
+      // Field that switches output based on which duplicate_id we're outputting
+      SwitchingField switching_field = 2;
+
+      // Field that outputs the same value no matter which duplicate_id we're on.
+      Expression consistent_field = 3;
+    }
+  }
+
+  message SwitchingField {
+    // Array that contains an expression to output per duplicate_id
+    // each `switching_field` must have the same number of expressions
+    // all expressions within a switching field must be the same type class but can differ in nullability.
+    // this column will be nullable if any of the expressions are nullable.
+    repeated Expression duplicates = 1;
+  }
+}
+
 // A relation with output field names.
 //
 // This is for use at the root of a `Rel` tree.
@@ -367,11 +395,11 @@ message Rel {
     ExtensionMultiRel extension_multi = 10;
     ExtensionLeafRel extension_leaf = 11;
     CrossRel cross = 12;
-
     //Physical relations
     HashJoinRel hash_join = 13;
     MergeJoinRel merge_join = 14;
     ExchangeRel exchange = 15;
+    ExpandRel expand = 16;
   }
 }
 
diff --git a/site/docs/relations/physical_relations.md b/site/docs/relations/physical_relations.md
index c3d8da102..fe311fbdf 100644
--- a/site/docs/relations/physical_relations.md
+++ b/site/docs/relations/physical_relations.md
@@ -206,6 +206,31 @@ The streaming aggregate operation leverages data ordered by the grouping express
 | Measures         | A list of one or more aggregate expressions. Aggregate expressions ordering requirements must be compatible with expected ordering. | Optional, required if no grouping sets. |
 
 
+## Expand Operation
+
+The expand operation creates duplicates of input records based on the Expand Fields. Each Expand Field can be a Switching Field or an expression. Switching Fields are described below.  If an Expand Field is an expression then its value is consistent across all duplicate rows.
+
+| Signature            | Value                                                                                                                                                                          |
+| -------------------- |--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Inputs               | 1                                                                                                                                                                              |
+| Outputs              | 1                                                                                                                                                                              |
+| Property Maintenance | Distribution is maintained if all the distribution fields are consistent fields with direct references. Ordering can only be maintained down to the level of consistent fields that are kept.|
+| Direct Output Order  | The expand fields followed by an i32 column describing the index of the duplicate that the row is derived from.                                                                                                                                           |
+
+### Expand Properties
+
+| Property  | Description                          | Required |
+| --------- |--------------------------------------| -------- |
+| Input     | The relational input.                | Required |
+| Direct Fields | Expressions describing the output fields.  These refer to the schema of the input.  Each Direct Field must be an expression or a Switching Field  | Required |
+
+### Switching Field Properties
+
+A switching field is a field whose value is different in each duplicated row.  All switching fields in an Expand Operation must have the same number of duplicates.
+
+| Property  | Description                          | Required |
+| --------- |--------------------------------------| -------- |
+| Duplicates | List of one or more expressions.  The output will contain a row for each expression. | Required |
 
 ## Hashing Window Operation