diff --git a/config/interpolate_funcs.go b/config/interpolate_funcs.go
index 5322e46c4..1b58ac93c 100644
--- a/config/interpolate_funcs.go
+++ b/config/interpolate_funcs.go
@@ -29,10 +29,12 @@ func init() {
 		"index":        interpolationFuncIndex(),
 		"join":         interpolationFuncJoin(),
 		"length":       interpolationFuncLength(),
+		"lower":        interpolationFuncLower(),
 		"replace":      interpolationFuncReplace(),
 		"split":        interpolationFuncSplit(),
 		"base64encode": interpolationFuncBase64Encode(),
 		"base64decode": interpolationFuncBase64Decode(),
+		"upper":        interpolationFuncUpper(),
 	}
 }
 
@@ -442,3 +444,29 @@ func interpolationFuncBase64Decode() ast.Function {
 		},
 	}
 }
+
+// interpolationFuncLower implements the "lower" function that does
+// string lower casing.
+func interpolationFuncLower() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			toLower := args[0].(string)
+			return strings.ToLower(toLower), nil
+		},
+	}
+}
+
+// interpolationFuncUpper implements the "upper" function that does
+// string upper casing.
+func interpolationFuncUpper() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			toUpper := args[0].(string)
+			return strings.ToUpper(toUpper), nil
+		},
+	}
+}
diff --git a/config/interpolate_funcs_test.go b/config/interpolate_funcs_test.go
index cafdf0564..f40f56860 100644
--- a/config/interpolate_funcs_test.go
+++ b/config/interpolate_funcs_test.go
@@ -644,6 +644,54 @@ func TestInterpolateFuncBase64Decode(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncLower(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${lower("HELLO")}`,
+				"hello",
+				false,
+			},
+
+			{
+				`${lower("")}`,
+				"",
+				false,
+			},
+
+			{
+				`${lower()}`,
+				nil,
+				true,
+			},
+		},
+	})
+}
+
+func TestInterpolateFuncUpper(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${upper("hello")}`,
+				"HELLO",
+				false,
+			},
+
+			{
+				`${upper("")}`,
+				"",
+				false,
+			},
+
+			{
+				`${upper()}`,
+				nil,
+				true,
+			},
+		},
+	})
+}
+
 type testFunctionConfig struct {
 	Cases []testFunctionCase
 	Vars  map[string]ast.Variable
diff --git a/website/source/docs/configuration/interpolation.html.md b/website/source/docs/configuration/interpolation.html.md
index 28d03790d..940839076 100644
--- a/website/source/docs/configuration/interpolation.html.md
+++ b/website/source/docs/configuration/interpolation.html.md
@@ -131,6 +131,8 @@ The supported built-in functions are:
       variable. The `map` parameter should be another variable, such
       as `var.amis`.
 
+  * `lower(string)` - returns a copy of the string with all Unicode letters mapped to their lower case.
+
   * `replace(string, search, replace)` - Does a search and replace on the
       given string. All instances of `search` are replaced with the value
       of `replace`. If `search` is wrapped in forward slashes, it is treated
@@ -147,6 +149,8 @@ The supported built-in functions are:
       `a_resource_param = ["${split(",", var.CSV_STRING)}"]`.
       Example: `split(",", module.amod.server_ids)`
 
+  * `upper(string)` - returns a copy of the string with all Unicode letters mapped to their upper case.
+
 ## Templates
 
 Long strings can be managed using templates. [Templates](/docs/providers/template/index.html) are [resources](/docs/configuration/resources.html) defined by a filename and some variables to use during interpolation. They have a computed `rendered` attribute containing the result.