diff --git a/build/config/substation.libsonnet b/build/config/substation.libsonnet
index a9fd38c5..3d4873a6 100644
--- a/build/config/substation.libsonnet
+++ b/build/config/substation.libsonnet
@@ -523,6 +523,18 @@
     },
     num: $.transform.number,
     number: {
+      max(settings={}): $.transform.number.maximum(settings=settings),
+      maximum(settings={}): {
+        local type = 'number_maximum',
+        local default = {
+          id: $.helpers.id(type, settings),
+          object: $.config.object,
+          value: null,
+        },
+
+        type: type,
+        settings: std.prune(std.mergePatch(default, $.helpers.abbv(settings))),
+      },
       math: {
         default: {
           object: $.config.object,
diff --git a/examples/config/transform/number/max/config.jsonnet b/examples/config/transform/number/max/config.jsonnet
new file mode 100644
index 00000000..42b3d359
--- /dev/null
+++ b/examples/config/transform/number/max/config.jsonnet
@@ -0,0 +1,11 @@
+// This example uses the `number_maximum` transform to return the larger
+// of two values, where one value is a constant and the other is a message.
+local sub = import '../../../../../build/config/substation.libsonnet';
+
+{
+  concurrency: 1,
+  transforms: [
+    sub.tf.num.max({ value: 0 }),
+    sub.tf.send.stdout(),
+  ],
+}
diff --git a/examples/config/transform/number/max/data.txt b/examples/config/transform/number/max/data.txt
new file mode 100644
index 00000000..a5c891fc
--- /dev/null
+++ b/examples/config/transform/number/max/data.txt
@@ -0,0 +1,4 @@
+0
+-1
+-1.1
+10
diff --git a/examples/config/transform/number/max/stdout.txt b/examples/config/transform/number/max/stdout.txt
new file mode 100644
index 00000000..2360ec2f
--- /dev/null
+++ b/examples/config/transform/number/max/stdout.txt
@@ -0,0 +1,4 @@
+0
+0
+0
+10
diff --git a/transform/number.go b/transform/number.go
index 51193fec..ec02512b 100644
--- a/transform/number.go
+++ b/transform/number.go
@@ -8,6 +8,31 @@ import (
 	"github.com/brexhq/substation/internal/errors"
 )
 
+// Use this config for any Number transform that only requires a single value.
+type numberValConfig struct {
+	Value float64 `json:"value"`
+
+	ID     string         `json:"id"`
+	Object iconfig.Object `json:"object"`
+}
+
+func (c *numberValConfig) Decode(in interface{}) error {
+	return iconfig.Decode(in, c)
+}
+
+// 0.0 is a valid value and should not be checked.
+func (c *numberValConfig) Validate() error {
+	if c.Object.SourceKey == "" && c.Object.TargetKey != "" {
+		return fmt.Errorf("object_source_key: %v", errors.ErrMissingRequiredOption)
+	}
+
+	if c.Object.SourceKey != "" && c.Object.TargetKey == "" {
+		return fmt.Errorf("object_target_key: %v", errors.ErrMissingRequiredOption)
+	}
+
+	return nil
+}
+
 type numberMathConfig struct {
 	ID     string         `json:"id"`
 	Object iconfig.Object `json:"object"`
diff --git a/transform/number_maximum.go b/transform/number_maximum.go
new file mode 100644
index 00000000..45f28ef4
--- /dev/null
+++ b/transform/number_maximum.go
@@ -0,0 +1,76 @@
+package transform
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"math"
+
+	"github.com/brexhq/substation/config"
+	iconfig "github.com/brexhq/substation/internal/config"
+	"github.com/brexhq/substation/message"
+)
+
+func newNumberMaximum(_ context.Context, cfg config.Config) (*numberMaximum, error) {
+	conf := numberValConfig{}
+	if err := iconfig.Decode(cfg.Settings, &conf); err != nil {
+		return nil, fmt.Errorf("transform number_maximum: %v", err)
+	}
+
+	if conf.ID == "" {
+		conf.ID = "number_maximum"
+	}
+
+	if err := conf.Validate(); err != nil {
+		return nil, fmt.Errorf("transform %s: %v", conf.ID, err)
+	}
+
+	tf := numberMaximum{
+		conf:     conf,
+		isObject: conf.Object.SourceKey != "" && conf.Object.TargetKey != "",
+	}
+
+	return &tf, nil
+}
+
+type numberMaximum struct {
+	conf     numberValConfig
+	isObject bool
+}
+
+func (tf *numberMaximum) Transform(ctx context.Context, msg *message.Message) ([]*message.Message, error) {
+	if msg.IsControl() {
+		return []*message.Message{msg}, nil
+	}
+
+	var value message.Value
+	if tf.isObject {
+		value = msg.GetValue(tf.conf.Object.SourceKey)
+	} else {
+		value = bytesToValue(msg.Data())
+	}
+
+	if !value.Exists() {
+		return []*message.Message{msg}, nil
+	}
+
+	flo64 := math.Max(value.Float(), tf.conf.Value)
+
+	if !tf.isObject {
+		s := numberFloat64ToString(flo64)
+		msg.SetData([]byte(s))
+
+		return []*message.Message{msg}, nil
+	}
+
+	if err := msg.SetValue(tf.conf.Object.TargetKey, flo64); err != nil {
+		return nil, fmt.Errorf("transform %s: %v", tf.conf.ID, err)
+	}
+
+	return []*message.Message{msg}, nil
+}
+
+func (tf *numberMaximum) String() string {
+	b, _ := json.Marshal(tf.conf)
+	return string(b)
+}
diff --git a/transform/number_maximum_test.go b/transform/number_maximum_test.go
new file mode 100644
index 00000000..1850d557
--- /dev/null
+++ b/transform/number_maximum_test.go
@@ -0,0 +1,158 @@
+package transform
+
+import (
+	"context"
+	"reflect"
+	"testing"
+
+	"github.com/brexhq/substation/config"
+	"github.com/brexhq/substation/message"
+)
+
+var _ Transformer = &numberMaximum{}
+
+var numberMaximumTests = []struct {
+	name     string
+	cfg      config.Config
+	test     []byte
+	expected [][]byte
+}{
+	// data tests
+	{
+		"data",
+		config.Config{
+			Settings: map[string]interface{}{
+				"value": 1,
+			},
+		},
+		[]byte(`0`),
+		[][]byte{
+			[]byte(`1`),
+		},
+	},
+	{
+		"data",
+		config.Config{
+			Settings: map[string]interface{}{
+				"value": -1,
+			},
+		},
+		[]byte(`0`),
+		[][]byte{
+			[]byte(`0`),
+		},
+	},
+	{
+		"data",
+		config.Config{
+			Settings: map[string]interface{}{
+				"value": -1.1,
+			},
+		},
+		[]byte(`0.1`),
+		[][]byte{
+			[]byte(`0.1`),
+		},
+	},
+	// object tests
+	{
+		"object",
+		config.Config{
+			Settings: map[string]interface{}{
+				"object": map[string]interface{}{
+					"source_key": "a",
+					"target_key": "a",
+				},
+				"value": 1,
+			},
+		},
+		[]byte(`{"a":0}`),
+		[][]byte{
+			[]byte(`{"a":1}`),
+		},
+	},
+	{
+		"object",
+		config.Config{
+			Settings: map[string]interface{}{
+				"object": map[string]interface{}{
+					"source_key": "a",
+					"target_key": "a",
+				},
+				"value": -1,
+			},
+		},
+		[]byte(`{"a":0}`),
+		[][]byte{
+			[]byte(`{"a":0}`),
+		},
+	},
+	{
+		"object",
+		config.Config{
+			Settings: map[string]interface{}{
+				"object": map[string]interface{}{
+					"source_key": "a",
+					"target_key": "a",
+				},
+				"value": -1.1,
+			},
+		},
+		[]byte(`{"a":0.1}`),
+		[][]byte{
+			[]byte(`{"a":0.1}`),
+		},
+	},
+}
+
+func TestNumberMaximum(t *testing.T) {
+	ctx := context.TODO()
+	for _, test := range numberMaximumTests {
+		t.Run(test.name, func(t *testing.T) {
+			tf, err := newNumberMaximum(ctx, test.cfg)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			msg := message.New().SetData(test.test)
+			result, err := tf.Transform(ctx, msg)
+			if err != nil {
+				t.Error(err)
+			}
+
+			var data [][]byte
+			for _, c := range result {
+				data = append(data, c.Data())
+			}
+
+			if !reflect.DeepEqual(data, test.expected) {
+				t.Errorf("expected %s, got %s", test.expected, data)
+			}
+		})
+	}
+}
+
+func benchmarkNumberMaximum(b *testing.B, tf *numberMaximum, data []byte) {
+	ctx := context.TODO()
+	msg := message.New().SetData(data)
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		_, _ = tf.Transform(ctx, msg)
+	}
+}
+
+func BenchmarkNumberMaximum(b *testing.B) {
+	for _, test := range numberMaximumTests {
+		tf, err := newNumberMaximum(context.TODO(), test.cfg)
+		if err != nil {
+			b.Fatal(err)
+		}
+
+		b.Run(test.name,
+			func(b *testing.B) {
+				benchmarkNumberMaximum(b, tf, test.test)
+			},
+		)
+	}
+}
diff --git a/transform/transform.go b/transform/transform.go
index 3f55f5de..ceff1e62 100644
--- a/transform/transform.go
+++ b/transform/transform.go
@@ -88,6 +88,8 @@ func New(ctx context.Context, cfg config.Config) (Transformer, error) { //nolint
 	case "meta_switch":
 		return newMetaSwitch(ctx, cfg)
 	// Number transforms.
+	case "number_maximum":
+		return newNumberMaximum(ctx, cfg)
 	case "number_math_addition":
 		return newNumberMathAddition(ctx, cfg)
 	case "number_math_division":