diff --git a/CHANGELOG.md b/CHANGELOG.md
index bfa60e1..e7b6f37 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 - Added support for parallel index builds
 - Added `l1_distance` function
 - Added element-wise multiplication for vectors
+- Added `sum` aggregate
 
 ## 0.4.4 (2023-06-12)
 
diff --git a/README.md b/README.md
index 377a5c2..cd9ef94 100644
--- a/README.md
+++ b/README.md
@@ -364,6 +364,7 @@ vector_norm(vector) → double precision | Euclidean norm
 Function | Description
 --- | ---
 avg(vector) → vector | arithmetic mean
+sum(vector) → vector | sum [unreleased]
 
 ## Installation Notes
 
diff --git a/sql/vector--0.4.4--0.5.0.sql b/sql/vector--0.4.4--0.5.0.sql
index b8d98be..1521589 100644
--- a/sql/vector--0.4.4--0.5.0.sql
+++ b/sql/vector--0.4.4--0.5.0.sql
@@ -11,3 +11,15 @@ CREATE OPERATOR * (
 	LEFTARG = vector, RIGHTARG = vector, PROCEDURE = vector_mul,
 	COMMUTATOR = *
 );
+
+CREATE FUNCTION vector_sum(double precision[]) RETURNS vector
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
+CREATE AGGREGATE sum(vector) (
+	SFUNC = vector_accum,
+	STYPE = double precision[],
+	FINALFUNC = vector_sum,
+	COMBINEFUNC = vector_combine,
+	INITCOND = '{0}',
+	PARALLEL = SAFE
+);
diff --git a/sql/vector.sql b/sql/vector.sql
index 9d98d03..55f830b 100644
--- a/sql/vector.sql
+++ b/sql/vector.sql
@@ -99,6 +99,9 @@ CREATE FUNCTION vector_avg(double precision[]) RETURNS vector
 CREATE FUNCTION vector_combine(double precision[], double precision[]) RETURNS double precision[]
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION vector_sum(double precision[]) RETURNS vector
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 -- aggregates
 
 CREATE AGGREGATE avg(vector) (
@@ -110,6 +113,15 @@ CREATE AGGREGATE avg(vector) (
 	PARALLEL = SAFE
 );
 
+CREATE AGGREGATE sum(vector) (
+	SFUNC = vector_accum,
+	STYPE = double precision[],
+	FINALFUNC = vector_sum,
+	COMBINEFUNC = vector_combine,
+	INITCOND = '{0}',
+	PARALLEL = SAFE
+);
+
 -- cast functions
 
 CREATE FUNCTION vector(vector, integer, boolean) RETURNS vector
diff --git a/src/vector.c b/src/vector.c
index 2ef05c7..8656468 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -1077,3 +1077,42 @@ vector_avg(PG_FUNCTION_ARGS)
 
 	PG_RETURN_POINTER(result);
 }
+
+/*
+ * Sum vectors
+ */
+PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_sum);
+Datum
+vector_sum(PG_FUNCTION_ARGS)
+{
+	ArrayType  *statearray = PG_GETARG_ARRAYTYPE_P(0);
+	float8	   *statevalues;
+	float8		n;
+	uint16		dim;
+	Vector	   *result;
+
+	/* Check array before using */
+	statevalues = CheckStateArray(statearray, "vector_sum");
+	n = statevalues[0];
+
+	/* SQL defines AVG of no values to be NULL */
+	if (n == 0.0)
+		PG_RETURN_NULL();
+
+	/* Create vector */
+	dim = STATE_DIMS(statearray);
+	CheckDim(dim);
+	result = InitVector(dim);
+	for (int i = 0; i < dim; i++)
+	{
+		result->x[i] = statevalues[i + 1];
+
+		/* Check for overflow */
+		if (isinf(result->x[i]))
+			float_overflow_error();
+
+		CheckElement(result->x[i]);
+	}
+
+	PG_RETURN_POINTER(result);
+}
diff --git a/test/expected/functions.out b/test/expected/functions.out
index 4008697..451762b 100644
--- a/test/expected/functions.out
+++ b/test/expected/functions.out
@@ -132,3 +132,27 @@ SELECT avg(v) FROM unnest(ARRAY['[1,2]'::vector, '[3]']) v;
 ERROR:  expected 2 dimensions, not 1
 SELECT vector_avg(array_agg(n)) FROM generate_series(1, 16002) n;
 ERROR:  vector cannot have more than 16000 dimensions
+SELECT sum(v) FROM unnest(ARRAY['[1,2,3]'::vector, '[3,5,7]']) v;
+   sum    
+----------
+ [4,7,10]
+(1 row)
+
+SELECT sum(v) FROM unnest(ARRAY['[1,2,3]'::vector, '[3,5,7]', NULL]) v;
+   sum    
+----------
+ [4,7,10]
+(1 row)
+
+SELECT sum(v) FROM unnest(ARRAY[]::vector[]) v;
+ sum 
+-----
+ 
+(1 row)
+
+SELECT sum(v) FROM unnest(ARRAY['[1,2]'::vector, '[3]']) v;
+ERROR:  expected 2 dimensions, not 1
+SELECT sum(v) FROM unnest(ARRAY['[3e38]'::vector, '[3e38]']) v;
+ERROR:  value out of range: overflow
+SELECT vector_sum(array_agg(n)) FROM generate_series(1, 16002) n;
+ERROR:  vector cannot have more than 16000 dimensions
diff --git a/test/sql/functions.sql b/test/sql/functions.sql
index 01a9bcc..83ee22e 100644
--- a/test/sql/functions.sql
+++ b/test/sql/functions.sql
@@ -34,3 +34,10 @@ SELECT avg(v) FROM unnest(ARRAY['[1,2,3]'::vector, '[3,5,7]', NULL]) v;
 SELECT avg(v) FROM unnest(ARRAY[]::vector[]) v;
 SELECT avg(v) FROM unnest(ARRAY['[1,2]'::vector, '[3]']) v;
 SELECT vector_avg(array_agg(n)) FROM generate_series(1, 16002) n;
+
+SELECT sum(v) FROM unnest(ARRAY['[1,2,3]'::vector, '[3,5,7]']) v;
+SELECT sum(v) FROM unnest(ARRAY['[1,2,3]'::vector, '[3,5,7]', NULL]) v;
+SELECT sum(v) FROM unnest(ARRAY[]::vector[]) v;
+SELECT sum(v) FROM unnest(ARRAY['[1,2]'::vector, '[3]']) v;
+SELECT sum(v) FROM unnest(ARRAY['[3e38]'::vector, '[3e38]']) v;
+SELECT vector_sum(array_agg(n)) FROM generate_series(1, 16002) n;