diff --git a/CHANGELOG.md b/CHANGELOG.md
index ac63ba196..2d8bd53c7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ Changelog for Cass Operator, new PRs should update the `main / unreleased` secti
 ```
 
 ## unreleased
+* [BUGFIX] [#355](https://github.com/k8ssandra/cass-operator/issues/335) Cleanse label names derived from cluster name, which can contain illegal chars for label names. 
 
 ## v1.11.0
 
diff --git a/pkg/oplabels/labels.go b/pkg/oplabels/labels.go
index 33feb550c..3c5e7cb2c 100644
--- a/pkg/oplabels/labels.go
+++ b/pkg/oplabels/labels.go
@@ -5,8 +5,9 @@ package oplabels
 
 import (
 	"fmt"
-
 	api "github.com/k8ssandra/cass-operator/apis/cassandra/v1beta1"
+	"regexp"
+	"strings"
 )
 
 const (
@@ -20,13 +21,13 @@ const (
 	CreatedByLabel             = "app.kubernetes.io/created-by"
 )
 
+var whitelistRegex = regexp.MustCompile(`(([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9])?`)
+
 func AddOperatorLabels(m map[string]string, dc *api.CassandraDatacenter) {
 	m[ManagedByLabel] = ManagedByLabelValue
 	m[NameLabel] = NameLabelValue
 	m[VersionLabel] = dc.Spec.ServerVersion
-
-	instanceName := fmt.Sprintf("cassandra-%s", dc.Spec.ClusterName)
-	m[InstanceLabel] = instanceName
+	m[InstanceLabel] = fmt.Sprintf("cassandra-%s", CleanLabelName(dc.Spec.ClusterName))
 
 	if len(dc.Spec.AdditionalLabels) != 0 {
 		for key, value := range dc.Spec.AdditionalLabels {
@@ -43,3 +44,12 @@ func HasManagedByCassandraOperatorLabel(m map[string]string) bool {
 	v, ok := m[ManagedByLabel]
 	return ok && v == ManagedByLabelValue
 }
+
+// CleanLabelName a valid label must be an empty string or consist of alphanumeric characters,
+// '-', '_' or '.', and must start and end with an alphanumeric.
+// Note: we apply a prefix of "cassandra-" to the cluster name value used as label name.
+// As such, empty string isn't a valid case.
+func CleanLabelName(labelName string) string {
+	var regexpResult = whitelistRegex.FindAllString(strings.Replace(labelName, " ", "", -1), -1)
+	return strings.Join(regexpResult, "")
+}
diff --git a/pkg/oplabels/labels_test.go b/pkg/oplabels/labels_test.go
new file mode 100644
index 000000000..d49828548
--- /dev/null
+++ b/pkg/oplabels/labels_test.go
@@ -0,0 +1,63 @@
+package oplabels
+
+import (
+	"github.com/stretchr/testify/require"
+	"regexp"
+	"strings"
+	"testing"
+)
+
+/**
+A valid label must be an empty string or consist of alphanumeric characters,
+'-', '_' or '.', and must start and end with an alphanumeric.
+*/
+func TestLabelNameClean(t *testing.T) {
+
+	var cleaned = CleanLabelName("TestCluster")
+	require.EqualValues(t, "TestCluster", cleaned,
+		"expect label name to not be cleaned as no need")
+
+	cleaned = CleanLabelName("Test Cluster")
+	require.EqualValues(t, "TestCluster", cleaned,
+		"expect space to be cleaned")
+
+	cleaned = CleanLabelName("+!*(-_)cor @#$%^&rect_ LABEL.name-1=<>_?,.")
+	require.EqualValues(t, "correct_LABEL.name-1", cleaned,
+		"expect label name w/ outlier chars to be cleaned")
+
+	cleaned = CleanLabelName("cor!@#$%^&*()rect__ LABEL.name")
+	require.EqualValues(t, "correct__LABEL.name", cleaned,
+		"expect label name w/ inside chars to be cleaned")
+
+	cleaned = CleanLabelName("correct")
+	require.EqualValues(t, "correct", cleaned,
+		"expect label name without chars to be correct")
+
+	cleaned = CleanLabelName("")
+	require.EqualValues(t, "", cleaned,
+		"expect label name as empty without chars to be correct")
+
+	cleaned = CleanLabelName("-_!@#$%-^&*.()<>?._-&*.")
+	require.EqualValues(t, "", cleaned,
+		"expect label name as empty as contains all bad chars")
+
+	cleaned = CleanLabelName("-_!@#$%-^&*.()<>?._-&*.X")
+	require.EqualValues(t, "X", cleaned,
+		"expect label name as last char only")
+
+	cleaned = CleanLabelName("Y-_!@#$%-^&*.()<>?._-&*.")
+	require.EqualValues(t, "Y", cleaned,
+		"expect label name as first char only")
+}
+
+func TestWhitelistRegex(t *testing.T) {
+
+	var whitelistRegex = regexp.MustCompile(`(([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9])?`)
+	var unclean = "+!*(-_)cor @#$%^&rect _ LABEL.name-1=<>_?,."
+	var regexpResult = whitelistRegex.FindAllString(strings.Replace(unclean, " ", "", -1), -1)
+	require.EqualValues(t, "correct_LABEL.name-1", strings.Join(regexpResult, ""))
+
+	unclean = "+!*(-_)cor @#$   %^&re _c-t-.LABEL.name-1=<>_?,."
+	regexpResult = whitelistRegex.FindAllString(strings.Replace(unclean, " ", "", -1), -1)
+	require.EqualValues(t, "corre_c-t-.LABEL.name-1", strings.Join(regexpResult, ""))
+}