diff --git a/DESCRIPTION b/DESCRIPTION
index 3616a59e5..7fad34ec9 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -53,7 +53,7 @@ VignetteBuilder:
 Config/Needs/dev: devtools, lifecycle, readr, glue, RcppTOML, smvr
 Config/Needs/lint: fs, lintr
 Config/Needs/website: etiennebacher/altdoc, future.apply
-Config/polars/lib-version: 1.7.1-rc.1
+Config/polars/lib-version: 1.9.0-rc.1
 Config/testthat/edition: 3
 Config/testthat/parallel: true
 Config/testthat/start-first: lazyframe-frame, *-s3-base, polars_options,
diff --git a/NEWS.md b/NEWS.md
index c91b7b110..21775f9af 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -2,6 +2,16 @@
 
 ## polars (development version)
 
+### New features
+
+- `as_polars_series()` on R factors now has an option `factor_as_enum` to convert
+  to a Polars Enum type. This can be set globally (for instance to convert all
+  factors in an R `data.frame` to enums with `as_polars_df()`) with
+  `options(polars.factor_as_enum = TRUE)` (#1723).
+
+- Converting a Polars enum to an R factor now preserves all levels, even if they
+  don't appear in the data (#1723).
+
 ## polars 1.8.0
 
 This is an update that corresponds to Python Polars 1.37.1.
diff --git a/R/as_polars_series.R b/R/as_polars_series.R
index 916872f05..efe3ae3c1 100644
--- a/R/as_polars_series.R
+++ b/R/as_polars_series.R
@@ -253,11 +253,22 @@ as_polars_series.raw <- function(x, name = NULL, ...) {
     wrap()
 }
 
+#' @param factor_as_enum `r lifecycle::badge("experimental")` if `FALSE`
+#' (default), R factors are converted to Polars [Categorical][pl__Categorical].
+#' If `TRUE`, they are converted to Polars [Enum][pl__Enum].
 #' @rdname as_polars_series
 #' @export
-as_polars_series.factor <- function(x, name = NULL, ...) {
+as_polars_series.factor <- function(x, name = NULL, ..., factor_as_enum = FALSE) {
+  if (missing(factor_as_enum)) {
+    opt <- getOption("polars.factor_as_enum")
+    if (!is.null(opt)) {
+      factor_as_enum <- opt
+    }
+  }
+  opt <- getOption("polars.factor_as_enum")
+
   PlRSeries$new_str(name %||% "", as.character(x))$cast(
-    pl$Categorical()$`_dt`,
+    if (isTRUE(factor_as_enum)) pl$Enum(levels(x))$`_dt` else pl$Categorical()$`_dt`,
     strict = TRUE
   ) |>
     wrap()
diff --git a/R/polars_options.R b/R/polars_options.R
index 18e70e01e..8816b4885 100644
--- a/R/polars_options.R
+++ b/R/polars_options.R
@@ -20,6 +20,9 @@
 #'   `compat_level` argument. See the documentation of those functions for details.
 #' * for all `to_r_vector.*` options, see arguments of [to_r_vector()][series__to_r_vector].
 #' * `df_knitr_print` (TODO: possible values??)
+#' * `factor_as_enum`: if `FALSE` (default), R factors are converted to Polars'
+#'   [Categorical][pl__Categorical]. If `TRUE`, they are converted to Polars'
+#'   [Enum][pl__Enum].
 #'
 #' @return
 #' `polars_options()` returns a named list where the names are option names and
@@ -47,7 +50,8 @@ polars_options <- function() {
     to_r_vector.decimal = getOption("polars.to_r_vector.decimal", "double"),
     to_r_vector.as_clock_class = getOption("polars.to_r_vector.as_clock_class", FALSE),
     to_r_vector.ambiguous = getOption("polars.to_r_vector.ambiguous", "raise"),
-    to_r_vector.non_existent = getOption("polars.to_r_vector.non_existent", "raise")
+    to_r_vector.non_existent = getOption("polars.to_r_vector.non_existent", "raise"),
+    factor_as_enum = getOption("polars.factor_as_enum", FALSE)
   )
 
   arg_match_compat_level(out[["compat_level"]], arg_nm = "compat_level")
@@ -74,6 +78,7 @@ polars_options <- function() {
     c("raise", "null"),
     arg_nm = "to_r_vector.non_existent"
   )
+  check_bool(out[["factor_as_enum"]], arg = "factor_as_enum")
   structure(out, class = "polars_options_list")
 }
 
diff --git a/R/series-to_r_vector.R b/R/series-to_r_vector.R
index f60442feb..a6c727b4f 100644
--- a/R/series-to_r_vector.R
+++ b/R/series-to_r_vector.R
@@ -15,6 +15,8 @@
 #' - Decimal: [double].
 #' - String: [character].
 #' - Categorical: [factor].
+#' - Enum: [factor], all categories (levels) are preserved, even if unobserved in
+#'   the data.
 #' - Date: [Date] or [data.table::IDate][data.table::IDateTime],
 #'   depending on the `date` argument.
 #' - Time: [hms::hms] or [data.table::ITime][data.table::IDateTime],
diff --git a/man/as_polars_series.Rd b/man/as_polars_series.Rd
index 56b60c4aa..b2efa375c 100644
--- a/man/as_polars_series.Rd
+++ b/man/as_polars_series.Rd
@@ -58,7 +58,7 @@ as_polars_series(x, name = NULL, ...)
 
 \method{as_polars_series}{raw}(x, name = NULL, ...)
 
-\method{as_polars_series}{factor}(x, name = NULL, ...)
+\method{as_polars_series}{factor}(x, name = NULL, ..., factor_as_enum = FALSE)
 
 \method{as_polars_series}{Date}(x, name = NULL, ...)
 
@@ -117,6 +117,10 @@ When not specified, name is set to an empty string.}
 
 \item{...}{Additional arguments passed to the methods.}
 
+\item{factor_as_enum}{\ifelse{html}{\href{https://lifecycle.r-lib.org/articles/stages.html#experimental}{\figure{lifecycle-experimental.svg}{options: alt='[Experimental]'}}}{\strong{[Experimental]}} if \code{FALSE}
+(default), R factors are converted to Polars \link[=pl__Categorical]{Categorical}.
+If \code{TRUE}, they are converted to Polars \link[=pl__Enum]{Enum}.}
+
 \item{strict}{A logical value to indicate whether throwing an error when
 the input \link{list}'s elements have different data types.
 If \code{FALSE} (default), all elements are automatically cast to the super type, or,
diff --git a/man/polars_options.Rd b/man/polars_options.Rd
index b2036d25d..acebf17f6 100644
--- a/man/polars_options.Rd
+++ b/man/polars_options.Rd
@@ -36,6 +36,9 @@ default value in parenthesis):
 \code{compat_level} argument. See the documentation of those functions for details.
 \item for all \verb{to_r_vector.*} options, see arguments of \link[=series__to_r_vector]{to_r_vector()}.
 \item \code{df_knitr_print} (TODO: possible values??)
+\item \code{factor_as_enum}: if \code{FALSE} (default), R factors are converted to Polars'
+\link[=pl__Categorical]{Categorical}. If \code{TRUE}, they are converted to Polars'
+\link[=pl__Enum]{Enum}.
 }
 }
 \examples{
diff --git a/man/series__to_r_vector.Rd b/man/series__to_r_vector.Rd
index 2037eec44..76d2c270a 100644
--- a/man/series__to_r_vector.Rd
+++ b/man/series__to_r_vector.Rd
@@ -132,6 +132,8 @@ depending on the \code{int64} argument.
 \item Decimal: \link{double}.
 \item String: \link{character}.
 \item Categorical: \link{factor}.
+\item Enum: \link{factor}, all categories (levels) are preserved, even if unobserved in
+the data.
 \item Date: \link{Date} or \link[data.table:IDateTime]{data.table::IDate},
 depending on the \code{date} argument.
 \item Time: \link[hms:hms]{hms::hms} or \link[data.table:IDateTime]{data.table::ITime},
@@ -143,7 +145,7 @@ depending on the \code{as_clock_class} argument.
 \item Duration: \link{difftime} or \link[clock:duration-helper]{clock_duration},
 depending on the \code{as_clock_class} argument.
 \item Binary: \link[blob:blob]{blob::blob}.
-\item Null: \link[vctrs:unspecified]{vctrs::unspecified}.
+\item Null: \link[vctrs:vctrs-unspecified]{vctrs::unspecified}.
 \item List, Array: \link[vctrs:list_of]{vctrs::list_of}.
 \item Struct: \link{data.frame} or \link[tibble:tbl_df-class]{tibble}, depending on the \code{struct} argument.
 }
diff --git a/src/rust/Cargo.lock b/src/rust/Cargo.lock
index 33678295d..53ddc52a7 100644
--- a/src/rust/Cargo.lock
+++ b/src/rust/Cargo.lock
@@ -2277,7 +2277,7 @@ checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
 
 [[package]]
 name = "r-polars"
-version = "1.7.1-rc.1"
+version = "1.9.0-rc.1"
 dependencies = [
  "ciborium",
  "either",
diff --git a/src/rust/Cargo.toml b/src/rust/Cargo.toml
index c31b5e8e5..2f94b5cfd 100644
--- a/src/rust/Cargo.toml
+++ b/src/rust/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "r-polars"
-version = "1.7.1-rc.1"
+version = "1.9.0-rc.1"
 edition = "2024"
 rust-version = "1.89.0"
 publish = false
diff --git a/src/rust/src/series/export.rs b/src/rust/src/series/export.rs
index eaed458bc..8fbc185c0 100644
--- a/src/rust/src/series/export.rs
+++ b/src/rust/src/series/export.rs
@@ -150,7 +150,7 @@ impl PlRSeries {
                     series.cast(&DataType::Float64).unwrap().f64().unwrap(),
                 ))),
                 DataType::Float64 => Ok(<Sexp>::from(Wrap(series.f64().unwrap()))),
-                DataType::Categorical(_, _) | DataType::Enum(_, _) => {
+                DataType::Categorical(_, _) => {
                     let r_func: FunctionSexp =
                         <Sexp>::from(savvy::eval_parse_text("as.factor")?).try_into()?;
                     let chr_vec =
@@ -159,6 +159,36 @@ impl PlRSeries {
                     let _ = args.add("x", chr_vec);
                     Ok(r_func.call(args)?.into())
                 }
+                DataType::Enum(_, mapping) => {
+                    // Build factor manually to preserve Enum's level order
+                    // Convert to physical representation and cast to u32
+                    let phys = series.to_physical_repr();
+                    let phys_u32 = phys.cast(&DataType::UInt32).map_err(RPolarsErr::from)?;
+                    let phys_ca = phys_u32.u32().map_err(RPolarsErr::from)?;
+                    let len = phys_ca.len();
+
+                    // Get physical codes (0-indexed) and convert to R's 1-indexed
+                    let mut codes = OwnedIntegerSexp::new(len)?;
+                    for (i, opt_v) in phys_ca.into_iter().enumerate() {
+                        match opt_v {
+                            Some(v) => codes.set_elt(i, (v + 1) as i32)?,
+                            None => codes.set_na(i)?,
+                        }
+                    }
+
+                    // Get categories from Enum mapping and set as levels
+                    let categories = unsafe {
+                        StringChunked::from_chunks(
+                            PlSmallStr::from_static("category"),
+                            vec![mapping.to_arrow(true)],
+                        )
+                    };
+                    let levels: Sexp = Wrap(&categories).into();
+                    codes.set_attrib("levels", levels)?;
+                    codes.set_class(["factor"])?;
+
+                    Ok(codes.into())
+                }
                 DataType::List(inner) => unsafe {
                     let len = series.len();
                     let mut list = OwnedListSexp::new(len, false)?;
diff --git a/tests/testthat/_snaps/as_polars_series.md b/tests/testthat/_snaps/as_polars_series.md
index ef72a9970..d05fb5b39 100644
--- a/tests/testthat/_snaps/as_polars_series.md
+++ b/tests/testthat/_snaps/as_polars_series.md
@@ -426,6 +426,30 @@
       	null
       ]
 
+# use option to convert factor to enum
+
+    Code
+      as_polars_series(factor(1:2))
+    Output
+      shape: (2,)
+      Series: '' [enum]
+      [
+      	"1"
+      	"2"
+      ]
+
+---
+
+    Code
+      as_polars_series(factor(1:2), factor_as_enum = FALSE)
+    Output
+      shape: (2,)
+      Series: '' [cat]
+      [
+      	"1"
+      	"2"
+      ]
+
 # as_polars_series.default throws an error
 
     Code
diff --git a/tests/testthat/_snaps/polars_options.md b/tests/testthat/_snaps/polars_options.md
index 88c90871c..3f2370e59 100644
--- a/tests/testthat/_snaps/polars_options.md
+++ b/tests/testthat/_snaps/polars_options.md
@@ -86,6 +86,14 @@
       Error in `polars_options()`:
       ! `to_r_vector.non_existent` must be one of "raise" or "null", not "foo".
 
+# options are validated by polars_options() polars.factor_as_enum
+
+    Code
+      print(polars_options())
+    Condition
+      Error in `polars_options()`:
+      ! `factor_as_enum` must be `TRUE` or `FALSE`, not the string "foo".
+
 # options for to_r_vector() works: polars.to_r_vector.uint8 = integer
 
     Code
diff --git a/tests/testthat/test-as_polars_series.R b/tests/testthat/test-as_polars_series.R
index e7bfaf598..a5ab22aa6 100644
--- a/tests/testthat/test-as_polars_series.R
+++ b/tests/testthat/test-as_polars_series.R
@@ -68,6 +68,16 @@ patrick::with_parameters_test_that(
   }
 )
 
+test_that("use option to convert factor to enum", {
+  withr::with_options(
+    list(polars.factor_as_enum = TRUE),
+    {
+      expect_snapshot(as_polars_series(factor(1:2)))
+      expect_snapshot(as_polars_series(factor(1:2), factor_as_enum = FALSE))
+    }
+  )
+})
+
 test_that("as_polars_series.default throws an error", {
   x <- 1
   class(x) <- "foo"
diff --git a/tests/testthat/test-dataframe-s3-base.R b/tests/testthat/test-dataframe-s3-base.R
index ffc127ef6..7c3d691b8 100644
--- a/tests/testthat/test-dataframe-s3-base.R
+++ b/tests/testthat/test-dataframe-s3-base.R
@@ -337,3 +337,36 @@ patrick::with_parameters_test_that(
     expect_snapshot(dat[[value]], error = TRUE)
   }
 )
+
+test_that("as.data.frame() and as.list() keep all levels of Enums", {
+  lev <- c("b", "a", "c")
+  dat <- pl$DataFrame(
+    x = factor(c("a", "b"), levels = lev)
+  )$cast(x = pl$Enum(lev))
+
+  expect_equal(
+    dat |>
+      as.data.frame() |>
+      getElement("x") |>
+      levels(),
+    lev
+  )
+
+  # Same with as.list()
+  expect_equal(
+    dat |>
+      as.list(as_series = FALSE) |>
+      getElement("x") |>
+      levels(),
+    lev
+  )
+
+  # Changing the levels works
+  expect_equal(
+    dat$cast(x = pl$Enum(c("c", "b", "a"))) |>
+      as.data.frame() |>
+      getElement("x") |>
+      levels(),
+    c("c", "b", "a")
+  )
+})
diff --git a/tests/testthat/test-polars_options.R b/tests/testthat/test-polars_options.R
index 9b72a8cd8..810a367e8 100644
--- a/tests/testthat/test-polars_options.R
+++ b/tests/testthat/test-polars_options.R
@@ -13,6 +13,7 @@ patrick::with_parameters_test_that(
     "polars.to_r_vector.as_clock_class",
     "polars.to_r_vector.ambiguous",
     "polars.to_r_vector.non_existent",
+    "polars.factor_as_enum",
   ),
   {
     withr::with_options(
diff --git a/tools/lib-sums.tsv b/tools/lib-sums.tsv
deleted file mode 100644
index d9e47a114..000000000
--- a/tools/lib-sums.tsv
+++ /dev/null
@@ -1,9 +0,0 @@
-url	sha256sum
-https://github.com/pola-rs/r-polars/releases/download/lib-v1.7.1-rc.1/libr_polars-1.7.1-rc.1-aarch64-apple-darwin.tar.gz	ee64b59078c50a840a6733acdd89dce0f77461640934a0411010b5bb4633eb6e
-https://github.com/pola-rs/r-polars/releases/download/lib-v1.7.1-rc.1/libr_polars-1.7.1-rc.1-aarch64-pc-windows-gnullvm.tar.gz	59c155f79fb60ed340609c75e94d557c83aef9dc8f560434205746ad7b14ee5b
-https://github.com/pola-rs/r-polars/releases/download/lib-v1.7.1-rc.1/libr_polars-1.7.1-rc.1-aarch64-unknown-linux-gnu.tar.gz	2a62077ef33fad74ed9a209cd877cf72bbf687c2c1ab766598d1726f28467100
-https://github.com/pola-rs/r-polars/releases/download/lib-v1.7.1-rc.1/libr_polars-1.7.1-rc.1-aarch64-unknown-linux-musl.tar.gz	8e95d759baf271e0aa95d9aea2fce7989ebe9ebf60176997ccc0da0c4d382dea
-https://github.com/pola-rs/r-polars/releases/download/lib-v1.7.1-rc.1/libr_polars-1.7.1-rc.1-x86_64-apple-darwin.tar.gz	a224783bea798004eb0300960e6db60e5e1d63e901a4ca513c50cdf4eef03326
-https://github.com/pola-rs/r-polars/releases/download/lib-v1.7.1-rc.1/libr_polars-1.7.1-rc.1-x86_64-pc-windows-gnu.tar.gz	a4dfdf9876023704cb4acaa8d1c7522cbceadab48ca945e2cf5a1e070edffc99
-https://github.com/pola-rs/r-polars/releases/download/lib-v1.7.1-rc.1/libr_polars-1.7.1-rc.1-x86_64-unknown-linux-gnu.tar.gz	ecf22bf86965a34433e103f2a57ce60cdc16981d5ea452adfc6c21be96d2a815
-https://github.com/pola-rs/r-polars/releases/download/lib-v1.7.1-rc.1/libr_polars-1.7.1-rc.1-x86_64-unknown-linux-musl.tar.gz	2c50c044ee4513cf7b3c02caa01237f2aada433acac2a9cfc838ef9dc615e729