diff --git a/include/dca/phys/parameters/output_parameters.hpp b/include/dca/phys/parameters/output_parameters.hpp
index 864a52421..c1b870074 100644
--- a/include/dca/phys/parameters/output_parameters.hpp
+++ b/include/dca/phys/parameters/output_parameters.hpp
@@ -14,6 +14,7 @@
 #ifndef DCA_PHYS_PARAMETERS_OUTPUT_PARAMETERS_HPP
 #define DCA_PHYS_PARAMETERS_OUTPUT_PARAMETERS_HPP
 
+#include <filesystem>
 #include <stdexcept>
 #include <string>
 #include "dca/io/io_types.hpp"
@@ -64,6 +65,12 @@ class OutputParameters {
   template <typename ReaderOrWriter>
   void readWrite(ReaderOrWriter& reader_or_writer);
 
+  // Throws std::invalid_argument if the parsed parameters describe state that cannot be
+  // used in a run (e.g. the configured output directory does not exist on disk). Intended
+  // to be called by Parameters::readInput on the rank that parsed the input file.
+  // Issue #300: surface bad input at parse time instead of crashing later in HDF5.
+  void validate() const;
+
   const std::string& get_directory() const {
     return directory_;
   }
@@ -272,6 +279,11 @@ void OutputParameters::readWrite(ReaderOrWriter& reader_or_writer) {
   }
 }
 
+inline void OutputParameters::validate() const {
+  if (!std::filesystem::exists(directory_))
+    throw std::invalid_argument("Output directory does not exist: " + directory_);
+}
+
 }  // namespace params
 }  // namespace phys
 }  // namespace dca
diff --git a/include/dca/phys/parameters/parameters.hpp b/include/dca/phys/parameters/parameters.hpp
index 56c4be6ff..57636ab0d 100644
--- a/include/dca/phys/parameters/parameters.hpp
+++ b/include/dca/phys/parameters/parameters.hpp
@@ -281,6 +281,7 @@ void Parameters<Concurrency, Threading, Profiler, Model, RandomNumberGenerator,
     read_obj.open_file(filename);
     this->readWrite(read_obj);
     read_obj.close_file();
+    OutputParameters::validate();
   }
 }
 
diff --git a/test/unit/phys/parameters/output_parameters/missing_directory.json b/test/unit/phys/parameters/output_parameters/missing_directory.json
new file mode 100644
index 000000000..1ff57317f
--- /dev/null
+++ b/test/unit/phys/parameters/output_parameters/missing_directory.json
@@ -0,0 +1,5 @@
+{
+    "output": {
+        "directory": "/nonexistent/path/for/dca_input_validation_test"
+    }
+}
diff --git a/test/unit/phys/parameters/output_parameters/output_parameters_test.cpp b/test/unit/phys/parameters/output_parameters/output_parameters_test.cpp
index a8f19a75b..7a9ac7cfb 100644
--- a/test/unit/phys/parameters/output_parameters/output_parameters_test.cpp
+++ b/test/unit/phys/parameters/output_parameters/output_parameters_test.cpp
@@ -12,6 +12,8 @@
 // TODO: Add tests for get_buffer_size, pack, unpack and writing.
 
 
+#include <stdexcept>
+
 #include "dca/config/haves_defines.hpp"
 #include "dca/phys/parameters/output_parameters.hpp"
 #include "dca/testing/gtest_h_w_warning_blocking.h"
@@ -88,3 +90,18 @@ TEST(OutputParametersTest, ReadAll) {
   EXPECT_TRUE(pars.dump_Gamma_lattice());
   EXPECT_TRUE(pars.dump_chi_0_lattice());
 }
+
+// Issue #300, bug #1: a non-existent output.directory should produce a clear error at
+// parameter-read time. readWrite() parses the directory string without touching the
+// disk; validate() is where the existence check and the throw live.
+TEST(OutputParametersTest, MissingDirectoryThrows) {
+  dca::io::JSONReader reader;
+  dca::phys::params::OutputParameters pars;
+
+  reader.open_file(DCA_SOURCE_DIR
+                   "/test/unit/phys/parameters/output_parameters/missing_directory.json");
+  pars.readWrite(reader);
+  reader.close_file();
+
+  EXPECT_THROW(pars.validate(), std::invalid_argument);
+}