Index: flang/include/flang/Runtime/memory.h
===================================================================
--- flang/include/flang/Runtime/memory.h
+++ flang/include/flang/Runtime/memory.h
@@ -36,6 +36,10 @@
   void operator()(A *p) { FreeMemory(p); }
 };
 
+template <typename A> struct OwningPtrDeleter<A[]> {
+  void operator()(A *p) { FreeMemory(p); }
+};
+
 template <typename A> using OwningPtr = std::unique_ptr<A, OwningPtrDeleter<A>>;
 
 template <typename A> class SizedNew {
Index: flang/runtime/environment.h
===================================================================
--- flang/runtime/environment.h
+++ flang/runtime/environment.h
@@ -37,6 +37,9 @@
   int listDirectedOutputLineLengthLimit;
   enum decimal::FortranRounding defaultOutputRoundingMode;
   Convert conversion;
+
+private:
+  const char *GetEnvFromEnvp(const char *name, std::size_t name_length);
 };
 extern ExecutionEnvironment executionEnvironment;
 } // namespace Fortran::runtime
Index: flang/runtime/environment.cpp
===================================================================
--- flang/runtime/environment.cpp
+++ flang/runtime/environment.cpp
@@ -7,7 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "environment.h"
+#include "memory.h"
 #include "tools.h"
+#include <cassert>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
@@ -69,10 +71,9 @@
   // TODO: Set RP/ROUND='PROCESSOR_DEFINED' from environment
 }
 
-const char *ExecutionEnvironment::GetEnv(
+const char *ExecutionEnvironment::GetEnvFromEnvp(
     const char *name, std::size_t name_length) {
   if (!envp) {
-    // TODO: Ask std::getenv.
     return nullptr;
   }
 
@@ -90,6 +91,39 @@
       return eq + 1;
     }
   }
+
   return nullptr;
 }
+
+static OwningPtr<char[]> NullTerminatedString(
+    const char *name, std::size_t name_length) {
+  OwningPtr<char[]> result{static_cast<char *>(std::malloc(name_length + 1))};
+  if (result) {
+    std::memcpy(result.get(), name, name_length);
+    result[name_length] = '\0';
+  }
+
+  return result;
+}
+
+const char *ExecutionEnvironment::GetEnv(
+    const char *name, std::size_t name_length) {
+  assert(name_length && "Invalid environment variable name");
+
+  const char *value{GetEnvFromEnvp(name, name_length)};
+  if (value) {
+    return value;
+  }
+
+  // Try to read the environment directly. This is especially useful when
+  // ProgramStart was not invoked at all, e.g. when the main program is not
+  // Fortran.
+  OwningPtr<char[]> cStyleName{NullTerminatedString(name, name_length)};
+  if (!cStyleName) {
+    std::fputs("Fortran runtime: out of memory for env var name\n", stderr);
+    return nullptr;
+  }
+
+  return std::getenv(cStyleName.get());
+}
 } // namespace Fortran::runtime
Index: flang/unittests/Runtime/CommandTest.cpp
===================================================================
--- flang/unittests/Runtime/CommandTest.cpp
+++ flang/unittests/Runtime/CommandTest.cpp
@@ -11,6 +11,7 @@
 #include "gtest/gtest.h"
 #include "flang/Runtime/descriptor.h"
 #include "flang/Runtime/main.h"
+#include <cstdlib>
 
 using namespace Fortran::runtime;
 
@@ -204,4 +205,18 @@
       RTNAME(EnvVariableLength)(*CharDescriptor("NAME "), /*trim_name=*/false));
 
   EXPECT_EQ(0, RTNAME(EnvVariableLength)(*CharDescriptor("     ")));
+  EXPECT_EQ(0, RTNAME(EnvVariableLength)(*CharDescriptor("")));
+
+  // Test a variable that's expected to exist in the environment but isn't
+  // passed into ProgramStart's envp argument.
+  char *path{std::getenv("PATH")};
+  auto expectedLen{static_cast<int64_t>(std::strlen(path))};
+  EXPECT_EQ(expectedLen, RTNAME(EnvVariableLength)(*CharDescriptor("PATH")));
+}
+
+TEST(EnvironmentVariablesNoProgStart, Length) {
+  // Test a variable that's expected to exist in the environment.
+  char *path{std::getenv("PATH")};
+  auto expectedLen{static_cast<int64_t>(std::strlen(path))};
+  EXPECT_EQ(expectedLen, RTNAME(EnvVariableLength)(*CharDescriptor("PATH")));
 }