diff --git a/pkg/migrations/op_common.go b/pkg/migrations/op_common.go
index 9ca96639..0b54d8fc 100644
--- a/pkg/migrations/op_common.go
+++ b/pkg/migrations/op_common.go
@@ -19,6 +19,7 @@ const (
 	OpNameCreateIndex  OpName = "create_index"
 	OpNameDropIndex    OpName = "drop_index"
 	OpNameRenameColumn OpName = "rename_column"
+	OpNameSetUnique    OpName = "set_unique"
 )
 
 func TemporaryName(name string) string {
@@ -98,6 +99,9 @@ func (v *Operations) UnmarshalJSON(data []byte) error {
 		case OpNameDropIndex:
 			item = &OpDropIndex{}
 
+		case OpNameSetUnique:
+			item = &OpSetUnique{}
+
 		default:
 			return fmt.Errorf("unknown migration type: %v", opName)
 		}
@@ -154,6 +158,9 @@ func (v Operations) MarshalJSON() ([]byte, error) {
 		case *OpDropIndex:
 			opName = OpNameDropIndex
 
+		case *OpSetUnique:
+			opName = OpNameSetUnique
+
 		default:
 			panic(fmt.Errorf("unknown operation for %T", op))
 		}
diff --git a/pkg/migrations/op_set_unique.go b/pkg/migrations/op_set_unique.go
new file mode 100644
index 00000000..9d5be29f
--- /dev/null
+++ b/pkg/migrations/op_set_unique.go
@@ -0,0 +1,66 @@
+package migrations
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"strings"
+
+	"github.com/lib/pq"
+
+	"pg-roll/pkg/schema"
+)
+
+type OpSetUnique struct {
+	Table   string   `json:"table"`
+	Columns []string `json:"columns"`
+}
+
+var _ Operation = (*OpSetUnique)(nil)
+
+func (o *OpSetUnique) Start(ctx context.Context, conn *sql.DB, schemaName string, stateSchema string, s *schema.Schema) error {
+	// create unique index concurrently
+	_, err := conn.ExecContext(ctx, fmt.Sprintf("CREATE UNIQUE INDEX CONCURRENTLY IF NOT EXISTS %s ON %s (%s)",
+		pq.QuoteIdentifier(IndexName(o.Table, o.Columns)),
+		pq.QuoteIdentifier(o.Table),
+		strings.Join(quoteColumnNames(o.Columns), ", ")))
+	return err
+}
+
+func (o *OpSetUnique) Complete(ctx context.Context, conn *sql.DB) error {
+	// create a unique constraint using the unique index
+	_, err := conn.ExecContext(ctx, fmt.Sprintf("ALTER TABLE IF EXISTS %s ADD CONSTRAINT %s UNIQUE USING INDEX %s",
+		pq.QuoteIdentifier(o.Table),
+		pq.QuoteIdentifier(UniqueConstraintName(o.Table, o.Columns)),
+		pq.QuoteIdentifier(IndexName(o.Table, o.Columns))))
+
+	return err
+}
+
+func (o *OpSetUnique) Rollback(ctx context.Context, conn *sql.DB) error {
+	// drop the index concurrently
+	_, err := conn.ExecContext(ctx, fmt.Sprintf("DROP INDEX CONCURRENTLY IF EXISTS %s",
+		IndexName(o.Table, o.Columns)))
+
+	return err
+}
+
+func (o *OpSetUnique) Validate(ctx context.Context, s *schema.Schema) error {
+	table := s.GetTable(o.Table)
+
+	if table == nil {
+		return TableDoesNotExistError{Name: o.Table}
+	}
+
+	for _, column := range o.Columns {
+		if table.GetColumn(column) == nil {
+			return ColumnDoesNotExistError{Table: o.Table, Name: column}
+		}
+	}
+
+	return nil
+}
+
+func UniqueConstraintName(table string, columns []string) string {
+	return "_pgroll_unique_" + table + "_" + strings.Join(columns, "_")
+}