diff --git a/core/math/expression.cpp b/core/math/expression.cpp
index 6d47fed1215..26b773a2242 100644
--- a/core/math/expression.cpp
+++ b/core/math/expression.cpp
@@ -359,7 +359,7 @@ Error Expression::_get_token(Token &r_token) {
 								} else if (c == '.') {
 									reading = READING_DEC;
 									is_float = true;
-								} else if (c == 'e') {
+								} else if (c == 'e' || c == 'E') {
 									reading = READING_EXP;
 									is_float = true;
 								} else {
@@ -385,7 +385,7 @@ Error Expression::_get_token(Token &r_token) {
 							} break;
 							case READING_DEC: {
 								if (is_digit(c)) {
-								} else if (c == 'e') {
+								} else if (c == 'e' || c == 'E') {
 									reading = READING_EXP;
 								} else {
 									reading = READING_DONE;
diff --git a/core/string/ustring.cpp b/core/string/ustring.cpp
index c879cf99008..637394324e9 100644
--- a/core/string/ustring.cpp
+++ b/core/string/ustring.cpp
@@ -4964,17 +4964,18 @@ bool String::is_valid_float() const {
 	bool numbers_found = false;
 
 	for (int i = from; i < len; i++) {
-		if (is_digit(operator[](i))) {
+		const char32_t c = operator[](i);
+		if (is_digit(c)) {
 			if (exponent_found) {
 				exponent_values_found = true;
 			} else {
 				numbers_found = true;
 			}
-		} else if (numbers_found && !exponent_found && operator[](i) == 'e') {
+		} else if (numbers_found && !exponent_found && (c == 'e' || c == 'E')) {
 			exponent_found = true;
-		} else if (!period_found && !exponent_found && operator[](i) == '.') {
+		} else if (!period_found && !exponent_found && c == '.') {
 			period_found = true;
-		} else if ((operator[](i) == '-' || operator[](i) == '+') && exponent_found && !exponent_values_found && !sign_found) {
+		} else if ((c == '-' || c == '+') && exponent_found && !exponent_values_found && !sign_found) {
 			sign_found = true;
 		} else {
 			return false; // no start with number plz
diff --git a/core/variant/variant_parser.cpp b/core/variant/variant_parser.cpp
index 3ce242d49c9..00d2c2c8b35 100644
--- a/core/variant/variant_parser.cpp
+++ b/core/variant/variant_parser.cpp
@@ -441,7 +441,7 @@ Error VariantParser::get_token(Stream *p_stream, Token &r_token, int &line, Stri
 								} else if (c == '.') {
 									reading = READING_DEC;
 									is_float = true;
-								} else if (c == 'e') {
+								} else if (c == 'e' || c == 'E') {
 									reading = READING_EXP;
 									is_float = true;
 								} else {
@@ -451,7 +451,7 @@ Error VariantParser::get_token(Stream *p_stream, Token &r_token, int &line, Stri
 							} break;
 							case READING_DEC: {
 								if (is_digit(c)) {
-								} else if (c == 'e') {
+								} else if (c == 'e' || c == 'E') {
 									reading = READING_EXP;
 								} else {
 									reading = READING_DONE;
@@ -1962,7 +1962,7 @@ Error VariantWriter::write(const Variant &p_variant, StoreStringFunc p_store_str
 		case Variant::FLOAT: {
 			String s = rtos_fix(p_variant.operator double());
 			if (s != "inf" && s != "inf_neg" && s != "nan") {
-				if (!s.contains_char('.') && !s.contains_char('e')) {
+				if (!s.contains_char('.') && !s.contains_char('e') && !s.contains_char('E')) {
 					s += ".0";
 				}
 			}
diff --git a/modules/gdscript/editor/gdscript_highlighter.cpp b/modules/gdscript/editor/gdscript_highlighter.cpp
index 9d90c35736b..acb74c1a6dc 100644
--- a/modules/gdscript/editor/gdscript_highlighter.cpp
+++ b/modules/gdscript/editor/gdscript_highlighter.cpp
@@ -355,11 +355,11 @@ Dictionary GDScriptSyntaxHighlighter::_get_line_syntax_highlighting_impl(int p_l
 				is_bin_notation = true;
 			} else if ((str[j] == 'x' || str[j] == 'X') && str[j - 1] == '0') {
 				is_hex_notation = true;
-			} else if (!((str[j] == '-' || str[j] == '+') && str[j - 1] == 'e' && !prev_is_digit) &&
+			} else if (!((str[j] == '-' || str[j] == '+') && (str[j - 1] == 'e' || str[j - 1] == 'E') && !prev_is_digit) &&
 					!(str[j] == '_' && (prev_is_digit || str[j - 1] == 'b' || str[j - 1] == 'B' || str[j - 1] == 'x' || str[j - 1] == 'X' || str[j - 1] == '.')) &&
-					!(str[j] == 'e' && (prev_is_digit || str[j - 1] == '_')) &&
+					!((str[j] == 'e' || str[j] == 'E') && (prev_is_digit || str[j - 1] == '_')) &&
 					!(str[j] == '.' && (prev_is_digit || (!prev_is_binary_op && (j > 0 && (str[j - 1] == '_' || str[j - 1] == '-' || str[j - 1] == '+' || str[j - 1] == '~'))))) &&
-					!((str[j] == '-' || str[j] == '+' || str[j] == '~') && !is_binary_op && !prev_is_binary_op && str[j - 1] != 'e')) {
+					!((str[j] == '-' || str[j] == '+' || str[j] == '~') && !is_binary_op && !prev_is_binary_op && str[j - 1] != 'e' && str[j - 1] != 'E')) {
 				/* This condition continues number highlighting in special cases.
 				1st row: '+' or '-' after scientific notation (like 3e-4);
 				2nd row: '_' as a numeric separator;
diff --git a/modules/gdscript/tests/scripts/parser/features/constants.gd b/modules/gdscript/tests/scripts/parser/features/constants.gd
index 013c9c074f1..62600eea441 100644
--- a/modules/gdscript/tests/scripts/parser/features/constants.gd
+++ b/modules/gdscript/tests/scripts/parser/features/constants.gd
@@ -4,6 +4,8 @@ func test():
 	const _VECTOR = Vector2(5, 6)
 	const _ARRAY = []
 	const _DICTIONARY = {"this": "dictionary"}
+	const _FLOAT1 = 1e2
+	const _FLOAT2 = 1E2
 
 	# Create user constants from built-in constants.
 	const _HELLO = PI + TAU
diff --git a/modules/text_server_adv/text_server_adv.cpp b/modules/text_server_adv/text_server_adv.cpp
index b6678986b07..527d2dce41f 100644
--- a/modules/text_server_adv/text_server_adv.cpp
+++ b/modules/text_server_adv/text_server_adv.cpp
@@ -6881,7 +6881,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		ar.lang.insert(StringName("sd_Arab_PK"));
 		ar.digits = U"٠١٢٣٤٥٦٧٨٩٫";
 		ar.percent_sign = U"٪";
-		ar.exp = U"اس";
+		ar.exp_l = U"اس";
+		ar.exp_u = U"اس";
 		num_systems.push_back(ar);
 	}
 
@@ -6912,7 +6913,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		pr.lang.insert(StringName("uz_Arab_AF"));
 		pr.digits = U"۰۱۲۳۴۵۶۷۸۹٫";
 		pr.percent_sign = U"٪";
-		pr.exp = U"اس";
+		pr.exp_l = U"اس";
+		pr.exp_u = U"اس";
 		num_systems.push_back(pr);
 	}
 
@@ -6930,7 +6932,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		bn.lang.insert(StringName("mni_Beng_IN"));
 		bn.digits = U"০১২৩৪৫৬৭৮৯.";
 		bn.percent_sign = U"%";
-		bn.exp = U"e";
+		bn.exp_l = U"e";
+		bn.exp_u = U"E";
 		num_systems.push_back(bn);
 	}
 
@@ -6946,7 +6949,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		mr.lang.insert(StringName("sa_IN"));
 		mr.digits = U"०१२३४५६७८९.";
 		mr.percent_sign = U"%";
-		mr.exp = U"e";
+		mr.exp_l = U"e";
+		mr.exp_u = U"E";
 		num_systems.push_back(mr);
 	}
 
@@ -6957,7 +6961,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		dz.lang.insert(StringName("dz_BT"));
 		dz.digits = U"༠༡༢༣༤༥༦༧༨༩.";
 		dz.percent_sign = U"%";
-		dz.exp = U"e";
+		dz.exp_l = U"e";
+		dz.exp_u = U"E";
 		num_systems.push_back(dz);
 	}
 
@@ -6970,7 +6975,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		sat.lang.insert(StringName("sat_Olck_IN"));
 		sat.digits = U"᱐᱑᱒᱓᱔᱕᱖᱗᱘᱙.";
 		sat.percent_sign = U"%";
-		sat.exp = U"e";
+		sat.exp_l = U"e";
+		sat.exp_u = U"E";
 		num_systems.push_back(sat);
 	}
 
@@ -6981,7 +6987,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		my.lang.insert(StringName("my_MM"));
 		my.digits = U"၀၁၂၃၄၅၆၇၈၉.";
 		my.percent_sign = U"%";
-		my.exp = U"e";
+		my.exp_l = U"e";
+		my.exp_u = U"E";
 		num_systems.push_back(my);
 	}
 
@@ -6993,7 +7000,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		ccp.lang.insert(StringName("ccp_IN"));
 		ccp.digits = U"𑄶𑄷𑄸𑄹𑄺𑄻𑄼𑄽𑄾𑄿.";
 		ccp.percent_sign = U"%";
-		ccp.exp = U"e";
+		ccp.exp_l = U"e";
+		ccp.exp_u = U"E";
 		num_systems.push_back(ccp);
 	}
 
@@ -7015,7 +7023,8 @@ void TextServerAdvanced::_insert_num_systems_lang() {
 		ff.lang.insert(StringName("ff_Adlm_SN"));
 		ff.digits = U"𞥐𞥑𞥒𞥓𞥔𞥕𞥖𞥗𞥘𞥙.";
 		ff.percent_sign = U"%";
-		ff.exp = U"e";
+		ff.exp_l = U"𞤉";
+		ff.exp_u = U"𞤉";
 		num_systems.push_back(ff);
 	}
 }
@@ -7029,8 +7038,8 @@ String TextServerAdvanced::_format_number(const String &p_string, const String &
 			if (num_systems[i].digits.is_empty()) {
 				return p_string;
 			}
-			res.replace("e", num_systems[i].exp);
-			res.replace("E", num_systems[i].exp);
+			res = res.replace("e", num_systems[i].exp_l);
+			res = res.replace("E", num_systems[i].exp_u);
 			char32_t *data = res.ptrw();
 			for (int j = 0; j < res.length(); j++) {
 				if (data[j] >= 0x30 && data[j] <= 0x39) {
@@ -7054,7 +7063,8 @@ String TextServerAdvanced::_parse_number(const String &p_string, const String &p
 			if (num_systems[i].digits.is_empty()) {
 				return p_string;
 			}
-			res.replace(num_systems[i].exp, "e");
+			res = res.replace(num_systems[i].exp_l, "e");
+			res = res.replace(num_systems[i].exp_u, "E");
 			char32_t *data = res.ptrw();
 			for (int j = 0; j < res.length(); j++) {
 				if (data[j] == num_systems[i].digits[10]) {
diff --git a/modules/text_server_adv/text_server_adv.h b/modules/text_server_adv/text_server_adv.h
index ab37abc6f7e..6561667e80e 100644
--- a/modules/text_server_adv/text_server_adv.h
+++ b/modules/text_server_adv/text_server_adv.h
@@ -147,7 +147,8 @@ class TextServerAdvanced : public TextServerExtension {
 		HashSet<StringName> lang;
 		String digits;
 		String percent_sign;
-		String exp;
+		String exp_l;
+		String exp_u;
 	};
 
 	Vector<NumSystemData> num_systems;
diff --git a/scene/resources/syntax_highlighter.cpp b/scene/resources/syntax_highlighter.cpp
index 7905acfd0e4..662bb3d60c9 100644
--- a/scene/resources/syntax_highlighter.cpp
+++ b/scene/resources/syntax_highlighter.cpp
@@ -302,7 +302,7 @@ Dictionary CodeHighlighter::_get_line_syntax_highlighting_impl(int p_line) {
 		}
 
 		// Check for dot or underscore or 'x' for hex notation in floating point number or 'e' for scientific notation.
-		if ((str[j] == '.' || str[j] == 'x' || str[j] == 'X' || str[j] == '_' || str[j] == 'f' || str[j] == 'e' || (uint_suffix_enabled && str[j] == 'u')) && !in_word && prev_is_number && !is_number) {
+		if ((str[j] == '.' || str[j] == 'x' || str[j] == 'X' || str[j] == '_' || str[j] == 'f' || str[j] == 'e' || str[j] == 'E' || (uint_suffix_enabled && str[j] == 'u')) && !in_word && prev_is_number && !is_number) {
 			is_number = true;
 			is_a_symbol = false;
 			is_char = false;
diff --git a/tests/core/math/test_expression.h b/tests/core/math/test_expression.h
index 8dbc5cae21a..7f660697db0 100644
--- a/tests/core/math/test_expression.h
+++ b/tests/core/math/test_expression.h
@@ -181,6 +181,9 @@ TEST_CASE("[Expression] Scientific notation") {
 	CHECK_MESSAGE(
 			expression.parse("2.e5") == OK,
 			"The expression should parse successfully.");
+	CHECK_MESSAGE(
+			expression.parse("2.E5") == OK,
+			"The expression should parse successfully.");
 	CHECK_MESSAGE(
 			double(expression.execute()) == doctest::Approx(200'000),
 			"The expression should return the expected result.");
diff --git a/tests/core/string/test_string.h b/tests/core/string/test_string.h
index 479f448f24d..d0b1bf8448e 100644
--- a/tests/core/string/test_string.h
+++ b/tests/core/string/test_string.h
@@ -1888,15 +1888,15 @@ TEST_CASE("[String] Join") {
 }
 
 TEST_CASE("[String] Is_*") {
-	static const char *data[13] = { "-30", "100", "10.1", "10,1", "1e2", "1e-2", "1e2e3", "0xAB", "AB", "Test1", "1Test", "Test*1", "文字" };
-	static bool isnum[13] = { true, true, true, false, false, false, false, false, false, false, false, false, false };
-	static bool isint[13] = { true, true, false, false, false, false, false, false, false, false, false, false, false };
-	static bool ishex[13] = { true, true, false, false, true, false, true, false, true, false, false, false, false };
-	static bool ishex_p[13] = { false, false, false, false, false, false, false, true, false, false, false, false, false };
-	static bool isflt[13] = { true, true, true, false, true, true, false, false, false, false, false, false, false };
-	static bool isaid[13] = { false, false, false, false, false, false, false, false, true, true, false, false, false };
-	static bool isuid[13] = { false, false, false, false, false, false, false, false, true, true, false, false, true };
-	for (int i = 0; i < 12; i++) {
+	static const char *data[] = { "-30", "100", "10.1", "10,1", "1e2", "1e-2", "1e2e3", "0xAB", "AB", "Test1", "1Test", "Test*1", "文字", "1E2", "1E-2" };
+	static bool isnum[] = { true, true, true, false, false, false, false, false, false, false, false, false, false, false, false };
+	static bool isint[] = { true, true, false, false, false, false, false, false, false, false, false, false, false, false, false };
+	static bool ishex[] = { true, true, false, false, true, false, true, false, true, false, false, false, false, true, false };
+	static bool ishex_p[] = { false, false, false, false, false, false, false, true, false, false, false, false, false, false, false };
+	static bool isflt[] = { true, true, true, false, true, true, false, false, false, false, false, false, false, true, true };
+	static bool isaid[] = { false, false, false, false, false, false, false, false, true, true, false, false, false, false, false };
+	static bool isuid[] = { false, false, false, false, false, false, false, false, true, true, false, false, true, false, false };
+	for (unsigned int i = 0; i < sizeof(data) / sizeof(data[0]); i++) {
 		String s = String::utf8(data[i]);
 		CHECK(s.is_numeric() == isnum[i]);
 		CHECK(s.is_valid_int() == isint[i]);